Because you are converting the entire matrix in to a categorical matrix, the categories for the entire matrix are common. If you want to have different categories for each column. you will have to convert each columm to caterogical separately.
a = repmat(1:10,10,1);
b = categorical(a)
b = 10×10 categorical array
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
categories(b(:,1))
ans = 10×1 cell array
{'1' }
{'2' }
{'3' }
{'4' }
{'5' }
{'6' }
{'7' }
{'8' }
{'9' }
{'10'}
c = array2table(a);
c = varfun(@categorical,c)
c = 10×10 table
categorical_a1 categorical_a2 categorical_a3 categorical_a4 categorical_a5 categorical_a6 categorical_a7 categorical_a8 categorical_a9 categorical_a10
______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ _______________
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
categories(c{:,1})
ans = 1×1 cell array
{'1'}
