[Numpy-discussion] creating mesh data from xyz data

Neil Martinsen-Burrell nmb@wartburg....
Tue Sep 8 12:51:10 CDT 2009


On 2009-09-08 10:38 , Christopher Barker wrote:
> Giuseppe Aprea wrote:
>> I have some files with data stored in columns:
>>
>> x1     y1     z1
>> x2     y2     z2
>> x3     y3     z3
>> x4     y4     z4
>> x5     y5     z5
>> I usually load data using 3 lists: x, y and z; I wonder if there is
>> any function which is able to take these 3 lists and return the right
>> inputs for matplotlib functions.
>
> There may b e some MPL utilities that help with this, so you may want to
> ask there, but:
>
> What you want to do depends on the nature of your data. If your data is
> on a rectangular structured grid, the you should use your knowledge of
> the data structure to re-create that structure to pass to MPL.

To expand on Chris's very nice explanation, if the data points are in 
"raster" order where x1 = x2 = ... = xn and so forth, then you can use 
reshape to get your arrays for matplotlib.  Here's an example:

 >>> x = [1]*5+[2]*5+[3]*5
 >>> y = [6,7,8,9,10]*3
 >>> z = range(15)
 >>> x,y,z
([1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3], [6, 7, 8, 9, 10, 6, 7, 
8, 9, 10, 6, 7, 8, 9, 10], [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 
13, 14])
 >>> plot_x = np.array(x).reshape(3,5)
 >>> plot_y = np.array(y).reshape(3,5)
 >>> plot_z = np.array(z).reshape(3,5)
 >>> plot_x,plot_y,plot_z
(array([[1, 1, 1, 1, 1],
        [2, 2, 2, 2, 2],
        [3, 3, 3, 3, 3]]), array([[ 6,  7,  8,  9, 10],
        [ 6,  7,  8,  9, 10],
        [ 6,  7,  8,  9, 10]]), array([[ 0,  1,  2,  3,  4],
        [ 5,  6,  7,  8,  9],
        [10, 11, 12, 13, 14]]))

-Neil


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