Marlene Heinrich
By Marlene Heinrich

How to make an easy plot with matplotlib

How to make an easy plot with matplotlib

What is matplotlib?

Matplotlib is a package that can be used to create plots or different form of

visualization of data.

Creating a simple 2d-Plot

As a firs step the package needs to be imported with:

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from matplotlib import pyplot as plt

Now we create the data we want to plot, so for example:

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x = [1, 2, 3, 4, 5, 6]

y = [1, 0, 3.5, 3, 2, 1]

To plot this data we need a simple command:

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plt.scatter(x, y, marker = 'x', color='red')

plt.show()

The scatter-function gives a simple representation of the datapoints and the

show-command is needed to actually see the plot.

To create a scientifically acceptable result some improvement has to be done:

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plt.title('Testplot') #Adds a title above the plot

plt.xlabel('x') #Add labels to the axis

plt.ylabel('y')

plt.grid(linestyle='dotted') #Add a major grid

plt.errorbar(x, y, xerr=0.1, yerr=0.1, marker='x', linewidth=0, elinewidth=1)

plt.show()

plt.savefig('testplot.pdf') #Save the plot as a PDF

A difference one should note, is that in this case we have used the

errorbar-function. Both, to plot and to add errorbars. Because of this the

linewidth had to be set to zero otherwise the points would have a connection

line. To still have errorbars the elinewidth hat to be set to something greater

zero, otherwise they would just disappear.

With just slight changes a lot of plots can be done using python!