Replace values in matrix with values based on look up table, without loop?

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Robert 2015-6-16

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https://ww2.mathworks.cn/matlabcentral/answers/224135-replace-values-in-matrix-with-values-based-on-look-up-table-without-loop

回答： Walter Roberson 2015-6-17

I'm new to this type of data manipulation, I have a large matrix with a set of values which I would like to convert to different values based on a table. I did a search for lookup tables, but did not find functions readily, is this something that requires one of the tool boxes? Thanks!

Talbot

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James Tursa 2015-6-16

Please post a short example showing the input data set and the result you are looking for.

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Answer 1

Walter Roberson 2015-6-17

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https://ww2.mathworks.cn/matlabcentral/answers/224135-replace-values-in-matrix-with-values-based-on-look-up-table-without-loop#answer_182942

在 MATLAB Online 中打开

mapfrom = [2.8 19 -3 pi 42 1];
mapto = [5 6 2 41 -pi 7];
%we need to get them in sorted order
[sortfrom, sortidx] = sort(mapfrom);
sortto = mapto(sortidx);

Now to look up,

MappedValues = interp1(sortfrom, sortto, ValuesToLooKUp, 'nearest');

The 'nearest' is not needed if all of the original values and all of the values to look up are integers, but if any of them are floating point then you need it because floating point values often differ in the last bit or two from what you think they are.