3 Excel COLUMNS x,y,z imported into work space as vectors, z is a function of x,y how do i get the data into a 2d lookup table

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stephen collier
stephen collier on 22 Nov 2021
Commented: stephen collier on 23 Nov 2021
Hi all, im sure this has been answered but i cant seem to find an answer to what is probably a simple answer. 3 columns of data, x,y,z
z is a function of x,y. im inporting the data as 3 vectors. i can seem to get it into the correct form for a look up table in simlink, My end goal is to be able to interpolate for any x,y input and get an aproxamated output for z,

Accepted Answer

Jon on 22 Nov 2021
Edited: Jon on 22 Nov 2021
Here is an example MATLAB script that you could run to assign the necessary variables in your base workspace before running your Simulink model. The idea is that you have to make a two dimensional array, where the rows correspond to your x values in your Excel Sheet and the columns the y values in your Excel Sheet, with the elements given by your third, z, column in your spreadsheet.
% script to put 2D look up table into base workspace before running Simulink
% read in the three columns of data from Excel, third column is function of
% first two
T = readtable('look2.xlsx');
% sort the rows of the table so that z values will be columnwise values of
% m by n look up array
T = sortrows(T,{'y','x'});
% find the unique x and y entries to be used for looking up values in two d
% array in Simulink
x = unique(T.x);
y = unique(T.y);
% determine the dimension of the look up array
m = numel(x); % number of unique x entries
n = numel(y); % number of unique y entries
% make 2d look up array Z to be used in Simulink from the z column
Z = reshape(T.z,m,n);

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More Answers (1)

stephen collier
stephen collier on 23 Nov 2021
Thanks Jon,
That works well, however when i substitute my own data i get a reshape error, error snip attached.
stephen collier
stephen collier on 23 Nov 2021
Thank you Jon,
your explanation has given me greater understanding of how the look up table works, it is possible to limit x and y their relationship is linear, x is an irridance plot any y is a temperature value. ill need to find another method

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