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
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()
plt.hlines. E.g. plt.hlines(y, range(1,5), range(2,6))
plt.step(x, y, where='post')
If you have non-uniformly spaced data points, you can use the drawstyle keyword argument for plot:
x = [1,2.5,3.5,4]
y = [0.002871972681775004, 0.00514787917410944,
0.00863476098280219, 0.012003316194034325]
plt.plot(x, y, drawstyle='steps-pre')
Also available are steps-mid and steps-post.
drawstyle documentation link. "‘steps’ is equivalent to ‘steps-pre’ and is maintained for backward-compatibility."There is a new plt.stairs method to complement plt.step:
plt.stairsand the underlyingStepPatchprovide a cleaner interface for plotting stepwise constant functions for the common case that you know the step edges.This supersedes many use cases of
plt.step, for instance when plotting the output ofnp.histogram.
Check out the official matplotlib gallery for how to use plt.stairs and StepPatch.
plt.step vs plt.stairsUse the original plt.step if you have reference points. Here the steps are anchored at [1,2,3,4] and extended to the left:
plt.step(x=[1,2,3,4], y=[20,40,60,30])
Use the new plt.stairs if you have edges. The previous [1,2,3,4] step points correspond to [1,1,2,3,4] stair edges:
plt.stairs(values=[20,40,60,30], edges=[1,1,2,3,4])
plt.stairs with np.histogramSince np.histogram returns edges, it works directly with plt.stairs:
data = np.random.normal(5, 3, 3000)
bins = np.linspace(0, 10, 20)
hist, edges = np.histogram(data, bins)
plt.stairs(hist, edges)
plt.stairs(). My version of matplotlib does not contain it. I have also a bunch of code for python 2.7, so migrating is not that easy.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.
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()
plt.stairs([1,2,3,4,5,6],[0,1,2,3,4,5,6]) , i.e between 0 and 1 the value is 1, between 1 & 2 is 2 etc. the step plot function refers (in my opinion) to midpoints, not to edges. The problem for me, is that stairs does not exist in python2In case someone just wants to stepify some data rather than actually plot it:
def get_x_y_steps(x, y, where="post"):
if where == "post":
x_step = [x[0]] + [_x for tup in zip(x, x)[1:] for _x in tup]
y_step = [_y for tup in zip(y, y)[:-1] for _y in tup] + [y[-1]]
elif where == "pre":
x_step = [_x for tup in zip(x, x)[:-1] for _x in tup] + [x[-1]]
y_step = [y[0]] + [_y for tup in zip(y, y)[1:] for _y in tup]
return x_step, y_step
