Rather than duplicating the same data in multiple places, use grouping variables to process the data by the desired categories/groups. See https://www.mathworks.com/help/matlab/ref/splitapply.html for a very similar type of dataset example.
NB that if you use the table instead of an array you get the benefit if handling disparate data types together (where in your data Gender, Smoker are prime categorical variables), you can do this with rowfun.
I just pointed another Q? in the same direction <here>
