MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi

Learn moreOpportunities for recent engineering grads.

Apply Today**New to MATLAB?**

Asked by Nav
on 5 May 2013

For some reason when i run this script x always equals one when it's suppose to be a matrix.

The program is for star dectection from the image and x suppose to be the threshold with steps.

stars=imread('stars.jpg'); GREY = rgb2gray(stars); figure,imshow(GREY); big = max( max (GREY)); %255 threshold = .4; bwimage = GREY >= threshold*big; figure(2),imshow(bwimage); step=0.01;

for x = [0.0:step:1.0] BW = GREY > big.*x; count = sum(BW>=x); end

Thanks ill greatly appreciate the help

*No products are associated with this question.*

Answer by Walter Roberson
on 5 May 2013

Accepted answer

"x" is used as a loop control variable. During the loop it will have only one value at a time; after the loop it will be the last value that it was assigned in the loop.

You have a problem that each iteration of the loop, you are overwriting "BW" and "count".

xvals = 0 : step: 1; numx = length(xvals); for K = 1 : numx x = xvals(K); BW = GREY > big.*x; count(K) = sum(BW(:)); end

Answer by the cyclist
on 5 May 2013

The way you have coded this, *x* is in a for loop, and the code will step through values of *x*, one by one, starting from 0 and ending at 1.

Instead, did you mean to simply make x a vector? Then you just need

x = 0.0 : step : 1.0;

without the loop.

## 0 Comments