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Matplotlib Annotate Text In A Plot Using Python

In this article, we will learn how to annotate text in Matplotlib plot using Python. But if we only add annotation text to a plot, it will not look that great. Because we want that annotation to point to a particular location in the plot. Right? So we will also be looking at how we can add arrows to go with these annotations. By using arrows, we will be able to point it to a location on the plot as well.

Now does that sound good for you? Great! So then let u begin!

First thing first. Let us learn what an annotation is. Alright? Because knowing what an annotation does to a plot will help us know how to use it. Right? So let us start fro there.

What Is Annotation?

Annotation is a piece of text that we can add to a plot to add give some explanation. So that is all there is to it.

But then you may ask why we want to text annotate a Matplotlib? After all, we already have a way to add text inside a plot in Matplotlib. Right? We have already seen how we can do that in our earlier article. So then why do we need annotation as well?

Well, there is a simple reason for that. So you see, using text( ) function provided by Matplotlib is fine for simple texts. But for larger texts, we want to go for annotations because we can use arrows here! So that way we can use larger texts but still point this text a point on the plot using arrows!

So that is the real benefit of using annotated text in Matplotlib plots rather than normal text( ) function. I hope this is clear to you by now!

So with that, let us see how we can text annotate a point in the Matplotlib plot.

How To Use Matplotlib To Annotate Text In A Plot

So how do we add annotation to a Matplotlib plot? Well using the annotate( ) function from the pyplot module, of course!

So the pyplot module provides us with an annotate( ) function as well! So using this, we can add annotations to our plot. But how does the signature of this function look like? Let us take a look at it:

annotate(text, xy, xytext, arrowprops)

So this is the basic signature of the annotate( ) function. But this signature is not all of it. It is missing few more arguments. But they are all optional. So we have skipped what is not required.

So what do these arguments mean? To understand, let us take a look at them one by one:

text - This is the annotation text
xy - This is the x & y co-ordinates of the point on our plot to which we will be adding the annotation
xytext - This is the x & y co-ordinates where we want our annotated text to appear
arrowprops - This will define the properties of our arrow

I know this is all looking overwhelming. But it will become clear to you once we looked at an example code using that. Alright? So let us look at that right now!

Matplotlib Annotate Text Example

So here is our example code:

import matplotlib.pyplot as plt
y = [8, 10, 11, 12, 10, 9, 10, 8, 7, 11, 10, 9]
plt.plot(y)
plt.annotate('this is the point I want to point!',
xy=(4, 10), xytext=(5, 10.75), arrowprops=dict(facecolor='red'))
plt.show()

As you can see, we are using a simple data set y with 12 values in it. We are then calling the normal plot( ) function to plot this data. But the real meat is in our 4th line where we are using our annotate( ) function.

So as you can see, we are passing a number of parameters here. The first is the text parameter which simply reads “this is the point I want to point!”.

The next is the xy parameter which is the point we want to annotate. This is followed by the xytext parameter which allows us to set the location where we wan our text to appear.

And finally we have the arrowprops parameter which allows us to set the arrow properties.

So using this code we get the following plot:

Matplotlib Plot With Annotate Text
Matplotlib Plot With Annotate Text

So there you have it. This is how you can use Python Matplotlib library to create a plot with annotated text. I hope it was easy enough for you. But if you have any questions, do let me know in the comments below and I will be happy to help.

So with that, I will end this tutorial now. Hope you have a nice day! 🙂

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Matplotlib Add Text Inside A Plot Using Python

In this article, we will learn how to add text inside a plot using Matplotlib. But not just that. We will also look at how we can position this text inside the plot.

In our earlier articles, we had already seen how we can add titles and axis labels to our plot. Right? So this article will be a follow up of that. But only that we will be adding text inside the plot itself. This is unlike others where we added labels and titles outside the plot.

So how do we go about doing this? How can we add text inside a plot? If we can, can it be positioned wherever we want within the plot? These are some of the questions we will be answering next!

So let us start with the first question:

How To Add Text Inside A Matplotlib Plot Using Python

So to answer this, let us draw a simple plot using the following code:

import matplotlib.pyplot as plt
import numpy as np
x = np.arange(0, 20, 1)
y = np.arange(0, 2, 0.1)
plt.plot(x, y)
plt.show()

So this will give us a simple plot with a linear line that looks like this:

A simple line plot
A simple line plot

Okay. This is great! But now how do we go about adding a piece of text inside this plot? Let me say I want a piece of text that reads “This is cool!” written above the blue line, but somewhere in the middle? Can I do that in Matplotlib?

The text( ) function

Of course you can! Matplotlib provides you with a very specific function for you to do just that! The function is called the text( ) function and it is part of the plt module of Matplotlib.

So what does the signature of this text( ) function look like? Here it is:

plt.text(x, y, text)

In the above text( ) function signature,w e see that it takes in 3 parameters – x, y, & text. But what do they do? Well, the parameters x & y gives the co-ordinates where the text is to be written. While the “text” parameter specifies the text we want to write!

So how does this all workout for us where we want to say “This is cool!” above the blue line? Well, first we need to set the x & y co-ordinates.

From the plot above, we can choose a value that is above the line and somewhere in the middle. Right? So what would be that value? Well how about it being 5 along the x-axis and 1 along the y-axis? In which case, we can call the text( ) function as follows:

plt.text(5, 1, 'This is cool!')

We will call this function just before plotting. So our final code will then become:

import matplotlib.pyplot as plt
import numpy as np
x = np.arange(0, 20, 1)
y = np.arange(0, 2, 0.1)
plt.text(5, 1, 'This is cool!')
plt.plot(x, y)
plt.show()

So how will the plot look like for this code? Take a look at it for yourself!

Matplotlib Add Text Inside A Plot
Matplotlib Add Text Inside A Plot

Now that is what we wanted right?!

So there you have it. This is how we can add text inside a plot in Matplotlib using Python. Hope it was pretty easy to follow. But if you have any questions, do let me know in the comments below. I will be more than happy to help!

So until next time, have a nice day! 🙂

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How To Plot Scatter Plot In Python Using Matplotlib

In this article, we will learn how to plot a Scatter plot in Python using Matplotlib. But before we do that, we will learn what a Scatter plot is and what all options are there for us to use. Sounds good? Great! Then let us start!

What Is A Scatter Plot?

A scatter plot is a type of plot that we can use to display values from two sets of data. So what happens is, we will take two sets of data of same length & pair them together. We then use this pair to plot the scatter plot. It is very important for you to remember here that both the data sets have to be of the same length!

But there is another thing to note here. It is that the scatter plot will have only points drawn and no lines in them. So in other words the points in the plot will not be connected together. But just the points scattered across the chart. Hence the name scatter plot!

What Is The Use Of A Scatter Plot?

We can use Scatter plot to see any correlation between two data sets. So what happens is, similar points get grouped together in the scatter plot. Now this can be a very valuable insight for us. Especially when looking at non linear relationships between the two datasets! Does that make sense?

So we can use a scatter plot to find any relationship between data points.

So now that we know the uses of a scatter plot, let us see how to plot it. But to do so, we need two sets of data. Right? So what do we do for that? Where can we find it?

How To Plot A Scatter Plot In Python

Here is what we will do. We will use our good old random function randn( ) from the Numpy library for that. Alright? So check this code:

import matplotlib.pyplot as plt
import numpy as np
x = np.random.randn(100)
y = np.random.randn(100)
plt.scatter(x, y);
plt.show()

So this is the code that will generate us a scatter plot using two sets of random data. But what is going on here? Let us go through the code line by line:

So in line 1 and 2, we are importing our Matplotlib and Numpy libraries.

But what is going on in line 3 & 4? Well, as I said earlier, we need two sets of data for our scatter plot. So we are using Numpy’s randn( ) to generate these data sets. We will assign them to variables x & y.

Next in line 5, we call our good old plt module’s scatter( ) function and passing x & y to it. So this is the function that will generate our scatter plot using x & y data!

Finally we call the usual plt.show( ) function to display our resulting scatter plot. So here is how it looks like:

A basic Scatter Plot With 100 variables
A basic Scatter Plot With 100 variables

So as you can see, there are 100 points taken from x & y variables to be plotted along the X & Y axis. So if there are any points that are similar, they will converge together here!

How To Change The Size Of A Marker

The above chart is all well and good, but is there a way to control the size, color & marker type in it? Well, lucky for us Matplotlib does give us an option for this. So to do so, we need to set the s, c & marker parameters in our plt.scatter( ) function!

So here is a simple example code that changes the size and color of our plot markers:

import matplotlib.pyplot as plt
import numpy as np
x = np.random.randn(100)
y = np.random.randn(100)
size = 20*np.random.randn(100)
colors = np.random.rand(100)
marker = "^"
plt.scatter(x, y, s=size, c=colors, marker=marker);
plt.show()

And here is how our final scatter plot would look like:

Scatter Plot with changed color, size & marker type
Scatter Plot with changed color, size & marker type

So there you have it! This is how we plot a Scatter Plot in Python. I hope this was easy enough for you to follow. But if you have any doubts, do let me know in the comments below. I will be more than happy to help!

Alright? So then see you until next time. take care! 🙂

What to learn how to plot a Pie chart using Matplotlib? Take a look at this!

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How To Plot Pie Chart In Python Using Matplotlib

In this article, we will take a look at how we can plot a pie chart in Python using Matplotlib. But we wont stop there. Because we will also be looking at how to create labels & it’s explode feature.

Plot Pie Chart In Python Using Matplotlib – The Basics

But before we do any of this, we first need to learn what a Pie Chart is. What is it used for. Because only after knowing this will be able to play with it. Does that make sense? Great! So then let us start from there!

What Is A Pie Chart?

A Pie Chart is a circular representation of data. Where we will show each data in the data set as a sector in the pie chart. Wait! How are we going to show the value of that data then? Well it is simple. Each of the sector’s arc size will show the value of that data!

Where Do We Use A Pie Chart?

Okay all that is well and good. But where do we use a Pie Chart? Well, a Pie Chart is very useful when we want to compare the sector size to the size of the Pie Chart. So in other words, it is useful when we want to compare a value against the total sum of all the values! Does that make sense?

How To Plot A Pie Chart In Python

Okay. Now that we know what a Pie Chart is, let us see how we can plot one using Python. Once again, Matplotlib library comes to our rescue!

So we can use our Matplotlib library to plot a Pie chart in Python. But how do we do that? Well, take a look at the code below for that:

import matplotlib.pyplot as plt
x = [10, 25, 18]
plt.pie(x)
plt.show()

So as you can see from the above code, we have 3 numbers in our data set x. Their values are 10, 25 & 18. So now we want to use these values to plot a Pie chart. To do that, we just call the plt module’s pie( ) function and pass x to it. It is as simple as that! So when we call the plt module’s show( ) function we get the following Pie Chart:

Basic Pie Chart Using Python
Basic Pie Chart Using Python

So as you can see above, we have a basic Pie Chart with 3 sectors – Orange, Green & Blue. But did you notice something here? Their size is not the same, In fact their size corresponds to the value of our x dataset. Right?

So that is what I meant when I said “Each of the sector’s arc size will show the value of that data”. Aha! Now it all makes sense. Right?

But there is something not right in the above Pie chart. Can you see what it is? Yes, the Pie chart is not exactly circular. Right? How do we fix that?

Plotting A Circular Pie Chart Using Python

Well, fixing it is actually quite simple. We just need to define our Plotting area to be a square and then it will correct itself! So if we modify the above code as follows:

import matplotlib.pyplot as plt
plt.figure(figsize=(4,4));
x = [10, 25, 18]
plt.pie(x)
plt.show()

It will get fixed!

Fixed To Be A Circle
Fixed To Be A Circle

Now it looks like a perfect circle. Great!

How Is the Sector Size Of A Pie Chart In Python Calculated

So we can see three sectors in the above Pie Chart. But how is it’s width calculated to fit into the circle? Well it is actually quite simple. The pie( ) function in Matplotlib uses the formula:

x/sum(X)

to find the sector size. Here x is the data value this sector represents & sum(X) is the sum of all the values in the data set. So in other words, we are calculating the percentage of this value with respect to the whole data set. Hope that made sense to you!

But even though we now have a good circular Pie chart, there are a few things missing. One are the labels. Won’t it be great if we could label each of the sectors in the Pie chart? Second, how about it display the percentage of each sector as well?

That is what we will fix in the next section.

How To Add Labels To Pie Chart In Python

So first, let us see how we can add labels to this Pie chart. Alright? So how do we do that. Well, it so happens that our Matplotlib library has a way to do that too! We just need to use the “labels” parameter when calling the plt.pie( ) function with appropriate labels. So how does the code then look like? Take a look at it yourself:

import matplotlib.pyplot as plt
plt.figure(figsize=(4,4));
x = [10, 25, 18]
labels = ['Bus', 'Car', 'Train']
plt.pie(x, labels=labels)
plt.show()

And the Pie chart created by this code looks like this:

Pie Chart With Labels Plotted Using Python
Pie Chart With Labels Plotted Using Python

So now we have our labels around the sectors of this Pie Chart. Perfect!

How To Add Percentage Values To Pie Chart In Python

Adding percentage values to this Pie Chart is also quite simple. We just need to call the autopct parameter and it will fill in the values for us! So the code to do that looks like this:

import matplotlib.pyplot as plt
plt.figure(figsize=(4,4));
x = [10, 25, 18]
labels = ['Bus', 'Car', 'Train']
plt.pie(x, labels=labels, autopct='%1.1f%%')
plt.show()

Here the value ‘%1.1f%% is the format specifier that tells Matplotlib to print the percentages in x.x% format!

So here is how the plot with percentage now looks like:

Pie Chart With Percentage Plotted
Pie Chart With Percentage Plotted

Finally, we will take a look at the Explode feature of Matplotlib.

Explode Feature Of Pie Chart Using Matplotlib

This feature will allow us to split the sector and move it slightly above it’s center. It is difficult to explain what I mean by this using words, so let me show you by directly using it:

import matplotlib.pyplot as plt
plt.figure(figsize=(4,4));
x = [10, 25, 18]
labels = ['Bus', 'Car', 'Train']
explode = [0.1, 0.3, 0.2]
plt.pie(x, labels=labels, explode=explode, autopct='%1.1f%%')
plt.show()

Here the “explode” values that we are passing tells the Pie chart to offset the sector by so much fraction from the center of the pie.

So here is how the final Pie Chart looks like:

Exploded Pie Chart
Exploded Pie Chart

So there you have it. That is how we can draw a Pie chart in Python using Matplotlib library. I hope I have covered all the things relevant to drawing these Pie charts. But if you have any doubts regarding these, do not hesitate to ask in the comments. I will be more than happy to help!

So until next time, take care! 🙂

Learn How To Plot Histograms Using Python

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How To Plot Bar Chart In Python Using Matplotlib

In this article, we will learn how to plot a Bar Chart in Python using Matplotlib library. In our earlier articles, we learnt how to plot a Histogram and line plots. So this is going to be a follow up on that. But this time with Bar Charts!

So are you ready to learn about it? Great! Then let us start right away!

Plot Bar Chart In Python Using Matplotlib – The Basics

So to begin with, we will start with the basics. Alright? Because if we get our basics right, everything else will become very clear. I hope you agree with me! So here is the first basic thing to know about:

What Is A Bar Chart?

A bar chart is a chart that uses rectangular bars whose length is equal to the value it represents. Now this bar can either be a vertical bar or a horizontal bar. Alright? So it can be used in either ways. But the main thing is that it’s width is the value that it represents!

So it is quite simple then. Right? But how are we going to plot a bar chart using Python? Any Guess? Yep, using our good old Matplotlib library!

So how does the code of a simple bar chart using Matplotlib look like? Let us take a look at it next!

Example Plot Of A Bar Chart In Python Using Matplotlib

So here is our example code that shows us how we can do this:

import matplotlib.pyplot as plt
plt.bar([10, 12, 15], [18, 6, 24])
plt.show()

Okay. It looks pretty straight forward. So what is going on here?

As you can see in the first line, we are importing the standard plt module from the Matplotlib library. Now this module is like the Swiss army knife of the library. Because this is the module that has all the plotting functions.

So in this case, since we need to plot a bar chart, we will call the bar( ) function! Alright? So that is what we did in line 2.

plt.bar([10, 12, 15], [18, 6, 24])

But what are those two list values we are passing here? They are the X & Y co-ordinates. So the first list [10, 12, 15] gives the x-axis co-ordinate values. It is where the left margin of our bars will be drawn. On the other hand, the second list [18, 6, 24] gives us the height of the bars!

And finally in line3, we call the plt.show( ) function that will display our bar chart!

So how does our final Bar Chart look like? Well, take a look at it for yourself!

Plot Of A Bar Chart In Python Using Matplotlib
Plot Of A Bar Chart In Python Using Matplotlib

So there you go! That is how we plot a bar chart in Python using Matplotlib. It is quite easy to plot. Right? But if you still have any doubts, do let me know in the comments below. I will be more than happy to help! 🙂

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How To Plot Histogram In Python Using Matplotlib

So in this article, we will take a look at how we can plot histogram in Python using Matplotlib library. Now this is some thing quite different from the basics of line plotting we have seen so far. So I know you will need some time to get through it. So what I will do is to go through it in an easy to understand way. Alright?

So relax, take a cup of coffee if you want to. As we will now look into the plot of histogram in Python using Matplotlib!

Plot Histogram In Python Using Matplotlib – The Basics

To get started, let us first learn a bit about what Histogram plot is. And then we will look at other questions. Like where it is used and how to draw it using Matplotlib. Okay? Great! So here we go!

What is an Histogram?

A histogram is a way to display frequencies of some thing. So how does it look like? In simple words, it is drawn using bars.

Oh wait a second! So does that mean that it is a kind of bar graph? Yeah you are right. Kind of!

So what happens is, the data that you want to show in an histogram is grouped together. But it does not mean that they are grouped randomly. But instead, similar data items are grouped together. Alright? Does that make sense? So when you plot, you will be plotting these grouped data on the chart. Okay?

Now there is one other thing. In Matplotlib, we call these groups of data as bins.

What are Histogram bins?

So a histogram bin is nothing but a group of similar data. That is all it is. So there is nothing really confusing about it!

Alright. So now that we know what a histogram bin in Matplotlib is, it is time for us to see an example of it. So how do we go about creating a plot of histogram in Python? Here is an example of it.

Plot Histogram In Python Using Matplotlib – Example

So we all know that to start a plot of something, we need data. Right? So how do we get this data? Since histogram is used to plot a lot of data, we cannot create it by hand. So what do we do then? We will have to take help of a library. Of course!

And what better library than NumPy to get a set of random numbers. Right? So that is what we will do. We will use Numpy to generate a bunch of random numbers.

But how many random numbers shall we use? 10, 50 or 100? Naah! We can surely go more than that. Right? So how about using 1000 random numbers? 😉

So here is the piece of code we will use to generate 1000 random numbers using Numpy!

import numpy as np
y = np.random.randn(1000)

That is it! That is all the code we need to create 1000 random numbers using Numpy! So easy. Right?

So now that we have our data ready, let us see how we can plot it as a Histogram using Python’s Matplotlib.

So the code to plot a histogram using Matplotlib looks like this:

import matplotlib.pyplot as plt
import numpy as np

y = np.random.randn(1000)
plt.hist(y);
plt.show()

That’s it! We just import pyplot module and call it’s hist( ) function with our data. And the Matplotlib library does the rest. It will go ahead and plot a Histogram in Python for us!

This is very easy right? And that is the beauty of Matplotlib library. The modules and functions are so well written that you can create beautiful histogram plot in Python easily!

So then how does the final output plot of the Histogram look like? Well, you see it for yourself!

Plot of Histogram Drawn In Python Using Matplotlib
Plot of Histogram Drawn In Python Using Matplotlib

Matplotlib Histogram Bins

Woah! What happened here? We gave it 1000 input data points right? What happened to all of it then? Well let me explain. Here is what Matplotlib has done.

It has taken our 1000 data input and grouped them together into 10 bins. And then it created the above histogram!

So why 10 bins? Why not 12 or 15 or any other number? Now that is a valid question for you to ask. So let me tell you why the number 10.

It is because that is the default number of bins Matplotlib will create for any number of input data you give to it. Okay? Does that make sense?

So in simple terms – Matplotlib took our 1000 data & grouped closer numbers together into 10 bins. It then went on to create the above histogram plot!

So that is all there is to it! But what if we want to have more than 10 bins? Well, we will come to that soon, but not now. Because it is going to need it’s own article that I will write next!

So see you in the next article!

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How To Use Different Line Color And Marker Color In Matplotlib

In this article, we will learn how to to set different line color and marker color in Matplotlib plot. But if have seen my earlier article, I showed you how we can set colors to markers. Right? So this will be a follow up on that article. Alright?

So what is the problem we are trying to solve here? Well you see, we want to have a plot with lines connecting markers. But then main thing is that we want different line color and the marker color in it! So how can we do that? Let me explain!

So first, let us take a look at our earlier plot. This is how it looked like, right?

Matplotlib plot with colored markers
Matplotlib plot with colored markers

So as you can see in the plot above, we had changed the color of the triangle markers to magenta color. Right? So what was the code we used to generate this plot? Let us take a look at it as well:

import matplotlib.pyplot as plt
x = range(1, 10)
plt.plot(x, [xi*1 for xi in x], '*')
plt.plot(x, [xi*2 for xi in x], '+')
plt.plot(x, [xi*3 for xi in x], 'm^')
plt.show()

So we used the color code ‘m‘ in the third plot to get the color. Right? But what is missing here? Well, you can see that there are no lines drawn. Correct? So how do we go about fixing that? And more importantly, how can we add lines with different colors?

Well, to do that we will need to use certain keywords in the plot( ) function! That is the key to solving this problem! Does that make sense? Great!

So then what keyword do we need to use? Well you see, Matplotlib gives us a lot of keywords to use when plotting. So there are special keys for setting line color as well as marker color!

But how do these keywords look like? Let me explain.

Keywords To Use For Different Line Color And Marker Color In Matplotlib

There are three keywords we can use to set the color of a line and the marker. They are:

color or c – So by using a color or c keyword in our plot( ) function, we can set the line color of a plot.

markeredgecolor – By using this keyword, we will tell Matplotlib what color to use to draw the edges of our marker.

markerfacecolor – By using this keyword, we can tell Matplotlib what color to use for the face of our marker.

These are the 3 keywords than we can use to set different line color and marker color in Matplotlib. So now that we know what to use, let us next see how we can use it. Alright?

What better way than to use our previous plot and to change it’s color? Right? So let us do just that!

Let us change the color of our plot line to be Yellow while the triangles to be Red with a green border. Alright? So how will our plot then look like? Any guess?

Well, take a look at it yourself below:

Different Line Color And Marker Color Plot image
Different Line Color And Marker Color Plot image

Woah! That is nice, right? We now have total control over the colors we can use in our plots, right? So what is the code change we did to get this? Take a look at the code for yourself!

import matplotlib.pyplot as plt
x = range(1, 10)
plt.plot(x, [xi*1 for xi in x], '*')
plt.plot(x, [xi*2 for xi in x], '+')
plt.plot(x, [xi*3 for xi in x], color='yellow', marker='^', markeredgecolor='green', markerfacecolor='red')
plt.show()

So there is a tiny little change we have done to get this working. As said earlier, we simply used the keywords to set the color like we want. And it did work as we wanted. Right?

Conclusion

So that is all there is to set different line color and marker color in Matplotlib. You just need to use the right keyword and it will work like a charm!

So with that, I will end this article now. But if you have any doubt about it, do let me know in the comment below. I will be more than happy to help!

So until next time, take care! 🙂

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How To Change Marker Style In Matplotlib

So in the previous article, we say how to change line style in Matplotlib. But in this article, we will take a look at how we can change the marker style in Matplotlib. So let us start with some idea about what these markers are in the first place. Shall we?

What Are Markers In Matplotlib Plots?

So for us to learn what markers are in Matplotlib plots, let us take a look at our previous example. Alright? Show this is the plot that we had in our previous example:

An example Matplotlib plot with 3 lines drawn from 3 sets of data
An example Matplotlib plot with 3 lines drawn from 3 sets of data

So as you can see here, we have 3 lines drawn using Matplotlib. Right? But how did we get these lines in the first place? Any guess?

To understand that, we need to take a look at the piece of code that generated this plot. So here is what that code looks like:

import matplotlib.pyplot as plt
x = range(1, 10)
plt.plot(x, [xi*1 for xi in x], '-.')
plt.plot(x, [xi*2 for xi in x], '--')
plt.plot(x, [xi*3 for xi in x], ':')
plt.show()

So as you can see, the three lines we have plotted are drawn using these 3 lines of code:

plt.plot(x, [xi*1 for xi in x], '-.')
plt.plot(x, [xi*2 for xi in x], '--')
plt.plot(x, [xi*3 for xi in x], ':')

And what is the data set used to plot these lines? There are 3 sets of data and they are:

[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
[3, 6, 9, 12, 15, 18, 21, 24, 27, 30]

So as you can see, the three data sets shown above is what resulted in the 3 lines above.

But here is the thing. The lines that we have drawn in the plot are nothing but connections to these points. Right?

So in Matplotlib, we call these points as Markers and the lines joining them as Segments.

Aha! Now you know what these markers are, right? But there is another important thing you should notice here. The plot we have in the above pic is made up of both Markers & Segments. So the above Matplotlib plot has both Markers & Segments in it!

Woah..! We didn’t knew that the plot had markers in it right? But where is it then? Why can’t we see it?

Well it is because the markers in this plot are drawn using their default style and hence it is not clearly visible. Wait, what is the default style of a marker then?

What Is The Default Style Of A Marker In Matplotlib Plot?

The default style of a Matplotlib Marker is to draw it as a point. And this is the reason why we are not able to see it. Because we are then connecting them by lines!

But then this begs us the next question:

What can we do to make the markers in Matplotlib visible?

So how are we going to show clearly then? Well, the answer to that once again lies in the parameters we pass to the plot( ) function.

Wait, so how will that look like then?

Well, instead of using the plot( ) function to draw default markers and lines, we do something else. We will ask Matplotlib not to use default markers and also not to draw the lines!

So then, how will that code look like? Well, take a look at it yourself!

import matplotlib.pyplot as plt
x = range(1, 10)
plt.plot(x, [xi*1 for xi in x], '*')
plt.plot(x, [xi*2 for xi in x], '+')
plt.plot(x, [xi*3 for xi in x], '^')
plt.show()

So when we run this piece of code, what do you think will the plot look like? Any guess?

Change Marker Style In Matplotlib
Change Marker Style In Matplotlib

Woah! Where did this nice little plot come from?! How did we get those cool looking stars and triangles in the plot? Huh?!

How To Change Marker Styles In Matplotlib

Well here the thing. When we used the marker style ‘*’, ‘+’ and ‘^’ symbol in our code, it got translated to that. Now that is one nice little feature that Matplotlib library is giving to us. Right?

So how do we know what all Marker styles are made available to us by Matplotlib then?

Well that is when this nifty table below will help you out! Take a look at it. It is showing you all the marker styles you can draw on your Python plot to make it look pretty!

Marker SymbolMarker Style
^Triangle Up
vTria. Down
<Triangle Left
>Tria. Right
1Tripod Down
2Tripod Up
3Tripod Left
4Tripod Right
pPentagon
sSquare
hHexagon
HRoated Hexagon
*Star
+Plus
Horizontal
DDiamond
dLean diamond
|Vertical Line
Available Marker Styles To Draw Using Matplotlib

And this is how you can get some nice little pretty plots using Matplotlib Python library. So I hope this was quite easy to understand for you. But if you still have any questions around it, do let me know. Because I will be more than happy to help! 🙂

Categories
DATA MINING DATA SCIENCE DATA VISUALIZATION MACHINE LEARNING PROGRAMMING PYTHON TUTORIALS

How To Change Line Style In Matplotlib

If you have been working with Matplotlib to plot lines, you might be looking for how you can style lines. Right? So if that is the case, they you have come to the right place. Because in this article, we will learn how to change line style in Matplotlib.

But before we do that, I hope you already know how to plot multiple lines on Matplotlib. But if you do not know, then take a look at the article linked above. That should get you going. Alright?

Okay then. With that, it is time for us to get started on changing the style of our lines now! Are you ready?

Drawing Multiple Lines Using Matplotlib

So as I said in the earlier section, we first need to have the code to draw multiple lines. Here is that code we have from our earlier article:

import matplotlib.pyplot as plt
x = range(1, 10)
plt.plot(x, [xi*1 for xi in x])
plt.plot(x, [xi*2 for xi in x])
plt.plot(x, [xi*3 for xi in x])
plt.show()

So this is the same piece of code we have taken from our earlier article. When we run this code, we get the following output:

Matplotlib multiple lines same graph
Drawing Multiple Lines Using Matplotlib

So as you can see from the above pic, we have 3 different lines plotted on the same graph. But what is even more important is that all these lines are in different color. That is good. Right?

But what we want to do now is to change the line style in this Matplotlib output. Correct? So how do we go abut doing that?

How To Change Line Style In Matplotlib?

With the basic multi line plot ready, let us now see how we can change the style of these lines.

So how do we go about doing this? Any guess? I want you to think a little bit to see if you can make a guess before you look for the answer. Alright? Just take a minute or two to think it over before you read further.

Okay. Here is what we can do to change the line style that we draw using Matplotlib:

Just like we could change the color of our lines ourselves, we can also change the style of these lines. So how did we change the color of our lines using Matplotlib to what we want, earlier? Yes, we passed in a new parameter to our plot( ) function. Right?

So in the same way, we can change the line style in Matplotlib as well. By passing our desired style as a parameter to our plot( ) function!

So how does that look like? Well, we just need to pass in the style we want as another plot( ) function parameter. So we modify our code in the plt.plot( ) function as shown below:

plt.plot(x, [xi*1 for xi in x], '-.')
plt.plot(x, [xi*2 for xi in x], '--')
plt.plot(x, [xi*3 for xi in x], ':')

So what happens when you do that? You have just changed the line style of the plots. So here is how it now looks like:

Change Line Style In Matplotlib by passing in the style as a parameter to the plot() function.
Change Line Style In Matplotlib by passing in the style as a parameter to the plot() function.

Now that looks like a perfect plot, isn’t it? But this begs us to ask the next question:

What Are The Options Available To Change The Line Style In Matplotlib

So there are 4 line styles that Matplotlib provides us to choose from. They are:

Style SymbolStyle Type
Solid Line
Dashed Line
-.Dash Dot Line
:Dotted Line
4 line styles available for us to choose from in Matplotlib

So if you choose from any one of these styles, you can get some pretty looking plots out there!

Conclusion

So that is all there is to changing the line style of a Matplotlib plot! You just have to add a new parameter to the plot( ) function with the style information. That is it and then it just works!

Pretty easy way to achieve what we want then, right? 😉 That is the beauty of Matplotlib library. It has so many interesting features with such a simple API!

So then what does our final code look like? Here it is:

import matplotlib.pyplot as plt
x = range(1, 10)
plt.plot(x, [xi*1 for xi in x], '-.')
plt.plot(x, [xi*2 for xi in x], '--')
plt.plot(x, [xi*3 for xi in x], ':')
plt.show()

So with that, I will end this article now. But if you still have any questions, do let me know in the comment below. I will be more than happy to help! Alright?

So until next time, take care guys and gals out there! Have a great day! 🙂

Categories
TUTORIALS

pytesseract.pytesseract.tesseractnotfounderror: tesseract is not installed or it’s not in your path

In this article, we see how to fix the error : “pytesseract.pytesseract.tesseractnotfounderror: tesseract is not installed or it’s not in your path“.

So are you trying to use the Tesseract tool to do OCR using Python? But some how end up with this error? If yes, then this article will help you in fixing this error.

But before I explain you on how to fix it, here is what we will do. Let me explain you about what is happening here in the first place. Alright? Because if you know what is happening, you will be able to fix similar errors in future as well.

It is not just sufficient to know how to fix a problem. But to know why it happened in the first place. Right? So we will do just that.

What Does The Error Mean?

So let us take a look at the error once again, shall we? Here is what the error looks like:

pytesseract.pytesseract.tesseractnotfounderror How To Fix It?
pytesseract.pytesseract.tesseractnotfounderror How To Fix It?
pytesseract.pytesseract.tesseractnotfounderror: tesseract is not installed or it's not in your path

Does that error message makes any sense to you? No? Actually it does. But only if you know more about how Python’s PyTesseract library.

You see, PyTesseract library is a Python wrapper that makes use of the Tessseract application installed on your computer. So for the PyTesseract library to work, it needs to hook in to the Tesseract app first. But to do that, it needs to know where to find it. Right?

So how does the PyTesseract library know where to find it? Well that is where the OS PATH variables come into picture.

The Python library looks for an OS PATH variable called tesseract. So it is in this variable does it expect to find the path to the Tesseract app.

But when the library cannot find this PATH variable, or the Tesseract app, it will throw the error:

pytesseract.pytesseract.tesseractnotfounderror: tesseract is not installed or it's not in your path

So now that you know the root cause, what is the solution?

How To Fix pytesseract.pytesseract.tesseractnotfounderror?

To fix this problem, you have to follow these few simple steps:

  1. Make sure that Tesseract application is installed.
  2. Make sure that the OS PATH variable tesseract is set to point to the above application file.
    • So if you are on Windows, the tesseract PATH variable will have a value something like this: C:\Program Files (x86)\Tesseract-OCR\tesseract.exe. To find this out, type the below command:
      • echo $tesseract
    • But if you are on Mac or Linux (eg: Ubuntu), it will look like this: /usr/local/bin/tesseract. To find this out, type the below command:
      • echo $tesseract

So that is it! That is how you fix the tesseractnotfounderror error on your Python program.

Hope this helps. Do let me know if you have any questions and I will be happy to answer. See you in the next article. Cheers!

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