Finding location of change of signs of a matrix's elements

Hi everbody, I have a matrix like this:

A=[0 0 0 0.33 0.33 0.33 0 0 0 -0.33 -0.33 -0.33 0 0 0];

How can i find location of change of signs? I get an error while using find and diff command. I think, i have made a mistake because of the < and > symbols. May you help me? Thanks.

Answer 1

[Walter Roberson]

find(diff(sign(A)))+1

to return the locations of the beginning of the new sign.

Note that this includes changing to 0, as 0 has a different sign than positive numbers or negative numbers.

[Volkan Yangin]

Thank you Mr. Robenson. I have just understood my mistake now.

[MA-Winlab]

@Roberson, I tried your approach for finding the locations of change from 0 to 1 and from 1 to 0, but they are in one array.

So, if I have this array and want to find the locations of change from 1 to 0 (returned in an array) and the locations of change from 1 to 0 (returned in a SEPRATE array), how can I modify this line?

Thank you

A=[0 0 0 1 1 1 0 0 0 1 1 1 0 0 0];

[MA-Winlab]

Update

I figured out how to do that (in my case, the vector of 0s and 1s has an even number):

OpenClose = find(diff(sign(A))) + 1;

OneToZero = OpenClose(1:2:end)

ZeroToOne = OpenClose(2:2:end)