Matlab Code summing terms of array - arrays

Question

I have a code that is supposed to do the following:
The first function called on, named CalcNum1.m, will find the sum of all the
values in any sized array using a for loop instead of the sum function. This sum divided
by 2 will be saved to the variable Num1.
Finally, in the second function named PrintTerms.m, reorder your terms using the
built in sort function. Now, find how many terms (starting with the first and the
smallest), when adding upon one another, are necessary to surpass the value of Num1.
Print to the user how many terms are necessary.
Here is my code for the main script:
B = input ('Enter matrix B');
[Num1,sum] = CalcNum1(B);
[Q] = PrintTerms(B, Num1);
And here is my code for the functions
function [sum, Num1] = CalcNum1(B)
n = numel(B);
sum1 =0;
for i = 1:n
sum1 = sum1 + B(i);
end
sum = sum1;
Num1 = sum/2;
end
function [Q] = PrintTerms( B, Num1 )
sort (B)
sum1 = 0;
i = 0;
count = 0;
while sum1<=Num1
i = i+1
sum1 = sum1 + B(i)
count = count+1
end
Q = count;
sum1
fprintf(' This many terms necessary %.2f',Q)
end

Answer 1

Try:
function [Num1, my_sum] = CalcNum1(B)
n = numel(B);
my_sum =0;
for i = 1:n
my_sum = my_sum + B(i);
end
Num1 = my_sum/2;
end
Note that I switched the output order, as you call it [Num1,sum] =
function count = PrintTerms( B, Num1 ) % No need for brackets when only single output
B = sort(B); % Need to save it in a new (or the same variable)
% sort(B) will only print the sorted vector
my_sum = 0;
ii = 0;
count = 0;
while my_sum <= Num1
ii = ii+1; % Use semicolons to supress output
my_sum = my_sum + B(ii);
count = count + 1; % Use space for better readability
end
fprintf(' This many terms necessary %.2f \n', count)
% Include \n to get a line shift
end
Use brackets when you type in B, like this: [1 2 3 4 2 3 4 23 12 32 12 2 3 6]
If you want it simpler, you could also use cumsum and avoid the loops. This is your entire last function (except the print part):
vec_sum = cumsum(sort(B)); % See documentation for explanation
count = find(vec_sum >= Num1,1) ; % the second input 1, is to only include the
% first element larger than Num1

Answer 2

Your PrintTerms function seems to work well. As possible problem is that, asuming Num1 is an arbitrary value, if it's so large that it's not reached even with all elements of B, you will try to pull a non-existent further element from B. To avoid that you can add a condition with if and a flag result to indicate whether you had success or not:
% [...]
success = 1; % for now
while (sum1 <= Num1)
ii = ii+1; % Use semicolons to supress output
if ii>length(B)
success = 0; % we ran out of terms
break; % exit while loop
end
sum1 = sum1 + B(ii);
count = count + 1; % Use space for better readability
end
if success
fprintf(' This many terms necessary %.2f', count)
else
fprintf(' The sum cannot be reached')
end
Also, note that sort(B) does not store the result. Use B = sort(B);