Debug this: for loop

Hi, I have a problem with for loop in my case

for i = 1:P
SrJasnosc(i) = props2(i).MeanIntensity;        
end

and next operation is

I = find(SrJasnosc > 400);

when those two parts is contain in funtion to analize series of pictures matlab give me an error:

??? Undefined function or variable "SrJasnosc".

Error in ==> srednia at 18

I = find(SrJasnosc > 400);

when I put it to command window to check on one picture is ok work fine, but otherwise its crush by error, after 3 hours of thinking on it I give up, please help, sorry for bad english.

code for function :

function out = srednia(poOdj, IMy)

[O P] = bwlabel(poOdj);

props2 = regionprops(O,IMy,'MeanIntensity');

for i = 1:P SrJasnosc(i) = props2(i).MeanIntensity; end

I = find(SrJasnosc > 400);

out = ismember(O, I);

Answer 1

[Matt Tearle]

Quick diagnostic: display the value of P (after it's returned by bwlabel)

Answer 2

[Jan]

Btw: This can be done more efficiently:

for i = 1:P
  SrJasnosc(i) = props2(i).MeanIntensity;
end

==>

SrJasnosc = [props2.MeanIntensity];

This method defines SrJasnosc even if props2 is an empty struct as long as it has the needed field.

Answer 3

[gck]

Its done, problem was the value of P, sometimes pictures are empty so in that situation P is < 1 so loop never start and "SrJasnosc" not existed, before the loop I put code "SrJasnosc = zeros(1,P);" and this is solve the problem.

Thanks for help and quick ansver !

[Matt Tearle]

Yup, that's what I was guessing

[Walter Roberson]

Please Accept Matt's answer.