What mistake I am making?

I have write a for loop to get the average of positive multiples of 7 from [ 2 14 28 -7 5 ], with using sum function.

function [avg] = avgpositive7multiples_for (m)

i = 1;
s = 0;
a = 0;
if m(m >= 0) 
	for t = 1:length(m)
        i = t(find(mod(t,7)==0));
		s = s + i;
		a = numel(i);
	end
end
avg = s/a;

Answer 1

[Voss]

Using a loop:

function [avg] = avgpositive7multiples_for (m)
s = 0;
a = 0;
for t = 1:length(m)
    if m(t) > 0 && mod(m(t),7) == 0
        s = s + m(t);
        a = a + 1;
    end
end
avg = s/a;

Using logical indexing:

avg = mean(m(m>0 & mod(m,7) == 0));

Answer 2

[DGM]

Try this

m = [ 2 14 28 -7 5 ];
avgpositive7multiples_for(m)

ans = 21

function [avg] = avgpositive7multiples_for(m)
    m = m(m >= 0); % remove nonpositive values
    m = m(find(mod(m,7)==0)); % extract only multiples of 7
    
    % calculate sum
    s = 0;
    for k = 1:length(m)
        s = s + m(k);
    end
    
    avg = s/numel(m);
end

[Manav Divekar]

Thank you that helped