Running into an error while splitting dataset into train and test?

I have a dataset for machine learning that I'm trying to split into train and test using the KFold method.

What I've done is:

cv = cvpartition(data, 'KFold', 5)

% isolate the first set of training data
trainData = data(training(cv, 1), :);

When I try to do the same for the test set

testData = data(test(cv,1), :);

I run into an error :

Subscripting into a table using one subscript (as in t(i)) or three or more subscripts (as in t(i,j,k)) is not supported. Always specify a row subscript

and a variable subscript, as in t(rows,vars).

Why does this happen and is there another way to do this?