Re: [Matplotlib-users] Plotting *lists of data* instead of *functions*...

[John H. <jdh...@ac...>]

>>>>> "seberino" == seberino  <seb...@sp...> writes:

    seberino> Stephen Thanks for the help.  The format of the data is
    seberino> ASCII files and/or Python arrays that contain (x, y)
    seberino> coordinates or (x, y, z) coordinates for 3D.

    seberino> For starters, what is best way to plot triples in this
    seberino> list?...

    seberino> [ (0, 0, 3.3), (0, 1, 4.4), (1, 0, 2.2), (1, 1, 2.34)]

    seberino> I want to duplicate color plot on screenshots page:
    seberino> http://matplotlib.sourceforge.net/screenshots/pcolor_demo_large.png

You have a 2x2 grid.  pcolor is a bit funny in that for an MxN grid it
only plots M-1 x N-1 rectangles since it doesn't know how to handle
the edges.  So it's a bit of a pathalogical case for pcolor.

Basically you need to transform your list of 3 tuples into 3 arrays
x,y,z, and then reshape the array.  Here I'll use imshow which
doesn't have the edge problem


    from matplotlib.matlab import *
    data = [ (0, 0, 3.3), (0, 1, 4.4), (1, 0, 2.2), (1, 1, 2.34)]
    x,y,z = zip(*data)
    z = array(z); z.shape = 2,2
    imshow(z, interpolation='nearest', extent=(0,1,0,1))
    show()

If you had a longer data sequence, say 5x5, you would use pcolor like

    from matplotlib.matlab import *
    data = ....
    x,y,z = zip(*data)
    x = array(x); x.shape = 5,5
    y = array(y); y.shape = 5,5
    z = array(z); z.shape = 5,5
    pcolor(x,y,z)
    show()


In short, there is nothing special about plotting "data" versus
"functions".  Both are simply cases of plotting 1-D or 2-D arrays as
far as matplotlib is concerned.  Your task is to get your data in to
the right array shape.

JDH