Your wording is rather poor. It looks like what you want to do is for eachunique value in the first column find the corresponding maximum in the second column. This is trivial to obtain withunique andaccumarray:
You can use 'sequentialfs' function in the Statistics and Machine Learning Toolbox in MATALB to do sequential feature selection and reduce the dimensionality of data.
Refer the below links to know more about Feature Selection in MATLAB:
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