Populating a 3D lookup table

I have a simple 3x512 array (x,y,z) in an ascii table file that is located in a directory.

I want to create Simulink lookup table that accepts values for y and z and returns the corresponding interpolated x value.

Is there a way that I can populate the lookup table with the contents of the array in the ascii file? Most examples I see involve manual entry of individual data triplets. I just want to load the file.

Thanks.

Answer 1

[Image Analyst]

A 3 x 512 array is a 2D array, not a 3D array. Assuming you've read your ASCII table into an array in your program (perhaps using csvread or dlmread), you could do something like (untested)

[rows columns] = size(array3x512);
for row = 1 : rows
  x = array3x512(row, 1);
  y = array3x512(row, 2);
  z = array3x512(row, 3);
  lut2D(y, z) = x;
end

Then later, when you have some arbitrary y and z that you want the x for, you just say

x = lut2d(y,z);

Of course you'll have to round all your indexes to integers - that's required if you want to do a look up table instead of interpolation. You may also have to figure out what to do if every single y and z pair is not represented.

Answer 2

[Stephen]

Thanks.

I'm sure your suggestion would work with a Matlab script, but I'm trying to use a Simulink lookup table.

Answer 3

[Stephen]

I decided just to create a function. I used SFTools to curve fit the data and SFTool was able to provide a function that fitted too.

Answer 4

[Richard Willey]

Hi Stephen

I did a webinar a couple years back focusing on using sftool to generate lookup tables for Simulink.

The webinar includes (what I hope is) some useful code that you can use to optimize the location of the break points for the resulting LUT.

The webinar is available at: <http://www.mathworks.com/company/events/webinars/wbnr40143.html?id=40143&p1=525984714&p2=525984732>

You can download the code from MATLAB Central

http://www.mathworks.com/matlabcentral/fileexchange/26021-optimizing-breakpoints-for-tables

Answer 5

[Stephen]

Thanks Richard, I will watch your webinar