in reply to Interpolating data using pdl

pdl> $x = sequence( 3, 3)-> float

pdl> p $x

[
 [0 1 2]
 [3 4 5]
 [6 7 8]
]


pdl> $i = PDL::IO::Image-> new_from_pdl( $x )

pdl> $i-> rescale(5, 5, 2)

pdl> $x_new = $i-> pixels_to_pdl

pdl> p $x_new

[
 [      0     0.4       1     1.6       2]
 [    1.2     1.6     2.2     2.8     3.2]
 [      3     3.4       4     4.6       5]
 [    4.8     5.2     5.8     6.4     6.8]
 [      6     6.4       7     7.6       8]
]

[download]

Note, that "float" is important instead of default "double". Also, check possible interpolation methods.

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Re^2: Interpolating data using pdl
by karthik248 (Acolyte) on Mar 15, 2017 at 16:35 UTC

    Many thanks for the solution.

    I might be able to use this. Can you also help me with the further processing?

    The data-values can be categorized into three ranges and now i have a pdl with data for each point(pixel) of the map(as described here). And now i have to plot these points onto a image, with different colors based on the ranges. Can you provide a script for generating such image.

[reply]

      Actually, looking back at results in my answer, this bilinear is "somewhat" strange (and other interpolation methods are probably useless for the given task). 

      pdl> $x = sequence 3,3

pdl> $y = zeroes 5,5

pdl> bilin2d( $x, $y )

pdl> p $y

[
 [  0 0.5   1 1.5   2]
 [1.5   2 2.5   3 3.5]
 [  3 3.5   4 4.5   5]
 [4.5   5 5.5   6 6.5]
 [  6 6.5   7 7.5   8]
]

      [download]

      That's better now. We can even visualize it with mesh3d [$y].

      karthik248, it's not clear what kind of plot do you mean? 3-D? Over-impose some visualization onto a world map? Or just 2-D image with 3 different colors?

[reply]
[d/l]
[select]
        Thanks for the update. I meant a 2-D image with RGB or ARGB.
[reply]

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