How count positive numbers, but when you get a negative, the sum stops. so then, sum the following sequence of positive numbers..

Example

v =

     1     1    -1     1     1     1    -1    -1     1
%sum the sequence of positive numbers that are together

sol =

     2     3     1

Regards Claudio

Answer 1

[Andrei Bobrov]

v = [1 1 -1 1 1 1 -1 -1 1];
z = v > 0;
id = find([true;diff(v.') ~= 0]);
k = diff([id;numel(v)+1]);
out = k(z(id));

or use Image Processing Toolbox

v = [1 1 -1 1 1 1 -1 -1 1]
z = v > 0;
s = regionprops(z, 'Area');;
out = [s.Area];

or

v = [1 1 -1 1 1 1 -1 -1 1];
v1 = [-v(1)*sign(v(1)),v,-v(end)*sign(v(end))];
out = strfind(v1,[1, -1])-strfind(v1,[-1 1]);

[Javier]

Thanks

Andrei Bobrov

You are the Best ¡

Answer 2

[Wayne King]

x = randn(100,1);
sum(x(x>0))

For an example with integers:

x = randi([-5 5],20,1);
sum(x(x>0))

[Javier]

Thanks, but I just want to sum the sequence of positive numbers that are together, not all positive

Regards Claudio

Answer 3

[Walter Roberson]

sum(x(1 : find(x <= 0, 1)))

or

sum(x .* cumprod(x > 0))

[Javier]

Thanks Walter, but I just want to sum the sequence of positive numbers that are together

Example

v =

     1     1    -1     1     1     1    -1    -1     1

%sum the sequence of positive numbers that are together

sol =

     2     3     1