How can one clear all the variables but the ones wanted [duplicate]

Question

Often when running long memory expensive programs I want to clear everything but some specific variables. If one wants to delete just some variables clear varA varB can be used, but what about deleting all but this specific variables?

Answer 1

As mentioned above, clearvars includes a syntax for keeping variables in the workspace while clearing the remainder:

a = 1; b = 1; c = 1; d = 1;
keepvars = {'c', 'd'};

clearvars('-except', keepvars{:});

Which functions as expected.

Like clear, it can also accommodate regexp matching:

a1 = 1; a2 = 1; b = 1; c = 1;
keepvars = 'a\d'; % regex pattern

clearvars('-except', '-regexp', keepvars);

Which retains a1 and a2, as expected.

Answer 2

Make use of the fact that both who and whos have return values that can be stored in variables. The former returns a cell array of strings, the latter a struct array. For what you need, the former will suffice:

%// don't delete these '
keepvars = {'varA','varB'};

%// delete these
delvars = setdiff(who,keepvars);
clear(delvars{:},'delvars');