I'm trying to create a code that doing something like this ......

Hello........ I'm trying to create a code that doing something like this

data=[1 1 1 -1 1 1 -1 -1 -1 1 1 1]

take the sequence of positive and negative data

= 3 -1 2 -3 3

and, take the position of the value when it changes from positive to negative

= 1 4 5 6 7 10

%----------------------------

I made this code, but only works for positive numbers....... =(

data=[1 1 1 -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));

Thanks for your help

Answer 1

[Guru]

You had the answer, just had to create a variable of the negative values. I am assuming that

v = data

So just change your code to this

data=[1 1 1 -1 1 1 -1 -1 -1  1 1 1]
z = v > 0;
id = find([true;diff(v.') ~= 0]);
k = diff([id;numel(v)+1]);
% Set all values as if they were negative 1, then assign those that are not 
out = -k; 
out(z(id)) = k(z(id));

Answer 2

[Jan]

See http://www.mathworks.com/matlabcentral/fileexchange/41813-runlength:

data   = [1 1 1 -1 1 1 -1 -1 -1  1 1 1];
[v, n] = RunLength(data);
neg    = v < 0;
n(neg) = -n(neg);

[Javier]

Thanks Jan Simon, but I think that my MEX version not support your code "RunLength =( " Warning: You are using gcc version "4.6.3-1ubuntu5)". The version currently supported with MEX is "4.3.4". For a list of currently supported compilers see: http://www.mathworks.com/support/compilers/current_release/