Variable definition in a simple function

Question

Haojie 2012-7-17

0
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Hi all, I have a very simple function and cant get it work. I try to let t0(1)=t(2), t0(2)=t(3)... and write this function below. However it will show an error when I type t0=resize(t); in the command window. I have already defined t in another function.

Error in ==> resize at 2
k=2;
??? Output argument "t0" (and maybe others) not assigned during call to
"D:\HJ\Documents\MATLAB\resize.m>resize".
function t0=resize(t)
k=1;
while (k<size(t));
t0(k)=t(k+1);
k=k+1;
end

Your help is much appreciated.

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Answer 1

Walter Roberson 2012-7-17

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size(t) is always going to return a vector, so your expression k<size(t) is going to be comparing k to a vector of values.

http://www.mathworks.com/help/techdoc/ref/if.html

An evaluated expression is true when the result is nonempty and contains all nonzero elements (logical or real numeric). Otherwise, the expression is false.

Therefor the "if" will be false if there is any dimension within t for which 1 < size(t) is false. Which would occur if t is a vector (row vector or column vector) as the other dimension of a vector is 1, and 1 < 1 is false.

If you examine your code, if the very first iteration of the "while" does not occur, then you do not create t0 at all.

I suggest you read about length()