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This should be easy but I have just started toying with matplotlib and python. I can do a line or a scatter plot but i am not sure how to do a simple step function. Any help is much appreciated.

x = 1,2,3,4
y = 0.002871972681775004, 0.00514787917410944, 0.00863476098280219, 0.012003316194034325
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What do you mean by a step function? Like a histogram? – wim Jan 19 at 5:14
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3 Answers

up vote 2 down vote accepted

It seems like you want step.

E.g. 

import matplotlib.pyplot as plt

x = [1,2,3,4] 
y = [0.002871972681775004, 0.00514787917410944, 
     0.00863476098280219, 0.012003316194034325]

plt.step(x, y)
plt.show()

enter image description here

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Thanks! It works. Any way to get rid of the vertical lines? – rhm2012 Jan 19 at 5:52
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Well, if you don't want any vertical lines, have a look at plt.hlines. E.g. plt.hlines(y, range(1,5), range(2,6)) – Joe Kington Jan 19 at 6:17
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up vote 0 down vote

Just draw two lines, one at y=0, and one at y=1, cutting off at whatever x your step function is for?

e.g. if you want to step from 0 to 1 at x=2.3 and plot from x=0 to x=5:

import matplotlib.pyplot as plt
#                                 _
# if you want the vertical line _|
plt.plot([0,2.3,2.3,5],[0,0,1,1])
#
# OR:
#                                       _
# if you don't want the vertical line _
#plt.plot([0,2.3],[0,0],[2.3,5],[1,1])

# now change the y axis so we can actually see the line
plt.ylim(-0.1,1.1)

plt.show()
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up vote 0 down vote

I think you want pylab.bar(x,y,width=1) or equally pyplot's bar method. if not checkout the gallery for the many styles of plots you can do. Each image comes with example code showing you how to make it using matplotlib.

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