Using a condition to plot with matplotlib

Question

I have a 2-D array and I need to plot columns x and y but only within a certain range of x. I know how to plot using the index but I need to specify the value of x. I have a few of those arrays so I am trying to find a way to do that without having to look at each one of them individually.

Here is an example:

array([[  4.40148390e+03,   1.13200000e+00],
       [  4.40248390e+03,   1.12200000e+00],
       [  4.40348440e+03,   1.11600000e+00],
       [  4.40448440e+03,   1.10600000e+00],
       [  4.40548490e+03,   1.09200000e+00],
       [  4.40648490e+03,   1.07700000e+00],
       [  4.40748540e+03,   1.08700000e+00],
       [  4.40848540e+03,   1.09400000e+00],
       [  4.40948580e+03,   1.10200000e+00],
       [  4.41048580e+03,   1.09500000e+00],
       [  4.41148630e+03,   1.12000000e+00]])

So let's say I only need 4402 < x < 4410 but I don't know the index. Can I put something like: plot(x, y, where(4402 < x < 4410))?

I feel like there is something obvious that I am missing here :p

@mtadd Can you please post that as an answer (and maybe add some text explaining it) — tacaswell
– tacaswell, Commented Apr 14, 2013 at 2:40

mtadd · Accepted Answer · 2013-04-14 03:07:12Z

5

You could use matplotlib to set limits on your x-axis so as not to display all the points in your data series. However, we can filter your numpy array above as follows:

a = array([[ .... ]])
x = a[:,0]
y = a[:,1]

filter = (x>4402)&(x<4410)

plot(x[filter],y[filter])

answered Apr 14, 2013 at 3:07

mtadd

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1 Comment

mtadd Over a year ago

If this answer is accepted, this question should be tagged numpy.

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