CODEWITHSUNDEEP
pythonmatplotlibplot
Pastafarian
Pastafarian

Reputation: 2150

Incorrect matplotlib plot

I've been trying to make a simple plot on matplotlib with the following set of datapoints, but I'm getting an incorrect plot which is utterly baffling. The plot includes points that aren't in the set of datapoints.

enter image description here

The set of points I'm plotting are:

[(0, 0), (3, 0), (0, 0), (2, 0), (0, 0), (3, 0), (1, 0), (7, 0), (2, 0), (0, 0), (5, 0), (2, 1), (10, 1), (1, 0), (1, 0), (8, 0), (3, 0), (1, 0), (2, 0), (2, 0), (1, 0), (6, 1), (3, 0), (3, 0), (12, 1), (3, 0), (0, 0), (2, 0), (0, 0), (2, 0), (3, 1), (0, 0), (4, 0), (4, 0), (2, 0), (2, 0)]

And I'm simply calling:

plt.plot(pts, 'ro')

I'd love to know how I'm going wrong here. Thanks in advance.

Upvotes: 0

Views: 7075

Answers (2)

user1706918
user1706918

Reputation:

Currently, matplotlib thinks that you're trying to plot each entry of the tuple against the index of the tuple. That is, your plot has the points (i, x_i) and (i, y_i) with 'i' going from 1 to 35.

As @jedwards pointed out, you could use the scatter function. Or, you could make the plot function explicitly plot (x_i, y_i) by extracting each element of the tuple as follows:

import matplotlib.pyplot as plt

data = [(0, 0), (3, 0), (0, 0), (2, 0), (0, 0), (3, 0), (1, 0), (7, 0), (2, 0), (0, 0), (5, 0), (2, 1), (10, 1), (1, 0), (1, 0), (8, 0), (3, 0), (1, 0), (2, 0), (2, 0), (1, 0), (6, 1), (3, 0), (3, 0), (12, 1), (3, 0), (0, 0), (2, 0), (0, 0), (2, 0), (3, 1), (0, 0), (4, 0), (4, 0), (2, 0), (2, 0)]
plt.plot([int(i[0]) for i in data], [int(i[1]) for i in data], 'or')

plt.xlim(-1, 8) # Sets x-axis limits
plt.ylim(-1, 2) # Sets y-axis limits
plt.show()      # Show the plot

Upvotes: 1

jedwards
jedwards

Reputation: 30250

"Set of points" makes me think you want a scatter plot instead. If you're expecting something like this:

Graph

Then you probably want pyplot's scatter() function.

import matplotlib.pyplot as plt

data = [(0, 0), (3, 0), (0, 0), (2, 0), (0, 0), (3, 0), (1, 0), (7, 0), (2, 0), (0, 0), (5, 0), (2, 1), (10, 1), (1, 0), (1, 0), (8, 0), (3, 0), (1, 0), (2, 0), (2, 0), (1, 0), (6, 1), (3, 0), (3, 0), (12, 1), (3, 0), (0, 0), (2, 0), (0, 0), (2, 0), (3, 1), (0, 0), (4, 0), (4, 0), (2, 0), (2, 0)]

x,y = zip(*data)

#plt.plot(data, 'ro')  # is the same as
#plt.plot(x, 'ro')     # this

plt.scatter(x, y)     # but i think you want scatter
plt.show()

For plot() note:

If x and/or y is 2-dimensional, then the corresponding columns will be plotted.

Upvotes: 0

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