Why is my if statement making the values of a previous array disappear?

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sasha
sasha 2014-6-17
评论： Image Analyst 2014-6-17
My code basically looks like:
for x = 1:xmax
for y = 1:ymax
for l = 1:xmax
for m = 1:ymax
d(x,y,l,m) = (x-l)^2 + (y-m)^2
if f(x,y,1) ~=f(x,y,5)
%lots of new defined values
else
break
end
end
end
end
end
There is no problem when I remove the if statement, I get the correct array for d. But when the if statement is there the output of d is all zeros. Does anyone know why d is not calculated when I have the conditional in there since it's outside of the if?

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回答（2 个）

A Jenkins
A Jenkins 2014-6-17
break will terminate your for loop, and it won't continue all the way to ymax.
Perhaps you mean you use continue? Or just leave the else case out altogether?
  1 个评论
sasha
sasha 2014-6-17
There was one more loop that I didn't put in that is in the code:
for t= 1:tmax
for x = 1:xmax
for y = 1:ymax
for l = 1:xmax
for m = 1:ymax
d(x,y,l,m) = (x-l)^2 + (y-m)^2
if f(x,y,1) ~=f(x,y,5)
%lots of new defined values
else
break
end
end
end
end
end
end
I want the if statement to hold for all x and y and I want the time loop to be stopped if that condition is no longer true.
Is this the correct way to write it?

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Image Analyst
Image Analyst 2014-6-17
How would the f array ever change? And, have you tried stepping through the code with the debugger? That's what I do, and everyone else would do. Try this: http://blogs.mathworks.com/videos/2012/07/03/debugging-in-matlab/
  2 个评论
sasha
sasha 2014-6-17
In the portion that I didn't write out because it's too long and not entirely relevant there is a section that says:
f(x,y,t+1) = f(x,y,t)+g(x,y,t)
where g(x,y,t) is also defined. I also start off defining f(x,y,1). So the f array starts off not the same and will eventually get to equilibrium.

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