The size of the indicated variable

Question

Yigit 2011-11-20

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Hi,

When I run the following code ;

i=0;
t0 = clock;
while etime(clock, t0) < 10
disp(clock);
pwm(i)=0;
i = i +1;
tic
while toc<secs
end
pwm(i)=1;
i = i +1;
tic
while toc<secs
end
end

I get the following warning ;

The size of the indicated variable or array appears to be changing with each loop iteration. Commonly, this message appears because an array is growing by assignment or concatenation.

and application hangs even if it's a very simple algorithm.

Any ideas ?

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Yigit 2011-11-20

forgot to mention ; variable "secs" is defined in the code, didn't post those parts not to cause pollution.

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Answer 1

Image Analyst 2011-11-20

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在 MATLAB Online 中打开

I don't know how big pwm might get. Maybe run it once to see. Let's say that it ends up being 100000 elements long. Then, before your while loop, you simply preallocate:

pwm = zeros(1, 100000);

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Image Analyst 2011-11-21

I can't run your code because secs is undefined. What value are you using for it?

Yigit 2011-11-22

secs change between 0.01 ~ 0.002

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Answer 2

Kostas 2011-11-20

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Is there any chance the variable secs to have such a little value that it is always litter than "toc"? In such a case your code goes into an infinite loop which cause it to hang.

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Yigit 2011-11-20

secs is between 0.02 ~ 0.06, can this be causing ?

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Answer 3

Jan 2011-11-21

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The code fails, because you try to access "pwm(i)" for i=0, but the index must be >= 1. When I start with "i=1;" the code runs successfully on my computer.

Where does the program fail on your computer? You can eitehr use the debugger or insert some disp command to check this.

I would avoid "tic; while toc<secs, end". A pause command would be smarter.