Passing strings into function i get 'too many input arguments'

I've written a function to calculate gpa. I would like to pass in any number of inputs into the function, for example gpa('a+', 'b-', 'a', 'c+').

The function works fine when I only input one letter grade, but any more than one and I get the error 'too many input arguments.'

I've duplicated the code and run it as a script with passing in the letter grades as part of the script and it works fine. Calling the function is when I have problems.

function grade_pt= gpa(grade_in)

%user inputs a string consisting of the letter grade including '+' or '-' %function returns the equivalent grade point

grade_in = {grade_in};

grades= {'a+','a', 'a-', 'b+', 'b', 'b-', 'c+', 'c', 'c-', 'd', 'f'};

eq_pt = {4, 4, 3.7, 3.3, 3, 2.7, 2.3, 2, 1.7, 1, 0};

res=zeros(length(grade_in),length(grades));

grdvec=zeros(1,length(grade_in));

for n = 1:length(grade_in);

res(n,:)= strcmpi(grade_in(n), grades);

grdvec(n)=eq_pt{res(n,:)==1};

grade_pt=sum(grdvec)/length(grade_in);

end

end

[dpb]

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