plot single row of 2d numpy array against 1d list

Question

I would like to plot a single row from a 2-dimensional numpy array against a 1d list in python. For example, I would like to plot using matplotlib row 'i' as below

  |0 0 0 0 0|
  |1 1 1 1 1|
i |2 2 2 2 2|
  |. . . . .|
  |n n n n n|

against

[0, 100, 200, 300, 400]

What I have currently is:

plt.plot(list1, 2dimArray[i])

but this is not working. I had this functionality working when I was plotting 1d lists against 1d lists but I had to go multidimensional and chose numpy.

Is there anyway to do this?

If A is your 2D array, and x your 1D list, does plt.plot(x, A[i,:]) works? — Charles Brunet
– Charles Brunet, Commented Apr 8, 2013 at 3:09

askewchan · Accepted Answer · 2013-04-08 19:45:04Z

2

Using the data from your comment below, this works for me:

In [1]: import numpy as np

In [2]: x = np.arange(0,1100,100)

In [3]: y = np.random.rand(6,11)

In [4]: i = 2

In [5]: plt.plot(x, y[i])
Out[5]: [<matplotlib.lines.Line2D at 0x1043cc790>]

plot of row 2

The the thing is that the x and y arguments to plot must have the same shape (or at least the same first entry to shape).

In [6]: x.shape
Out[6]: (11,)

In [7]: y.shape
Out[7]: (6, 11)

In [8]: y[i].shape
Out[8]: (11,)

Perhaps one of your items generated by your program doesn't actually have the shape you believe it does?

This should also work if you use a list together with a numpy array (plt.plot will probably convert the list to an array):

In [9]: xl = range(0, 1100, 100)

In [10]: plt.plot(xl, y[i])
Out[10]: [<matplotlib.lines.Line2D at 0x10462aed0>]

edited Apr 8, 2013 at 19:45

answered Apr 8, 2013 at 3:15

askewchan

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6 Comments

sgchako Over a year ago

This is the error I am getting: ValueError: x and y must have same first dimension

askewchan Over a year ago

Can you tell us what b.shape and a.share are?

sgchako Over a year ago

x: 1d list constructed as such [0, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000] y: 2dim array constructed as such np.zeros( (6,11) )

askewchan Over a year ago

@user1535701 I can still get it to work using the data you supply. See my edit. Are you sure the shapes match?

sgchako Over a year ago

could it have to do with the fact that my y variable is an array and my x variable is a list? or do the two play nicely with one another with respect to plotting?

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