why embedded matlab function failed to determine the size of expression

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yana osman
yana osman 2012-7-18
Hi all,
u is an input from the output of continous state.so, for each time (1 x 3) matrix will come out, so
u matrix = 1 x 3
Mean = 1 x 450
is a mean of samples.This input from workspace which consist 150 times with 3 variables so its matrix is (1 x 450). but we only need (1 x 3) matrix to evaluate for each time
Std = 1 x 450
is a standard deviation of samples.Same description as above(mean)
Xnew = 1x3
is an outpyt from the equation Xnew = u-mean/std
Example;
for time 1
Xnew = u-Mean(1,1:3)
time 2
Xnew = u-Mean(1,4:6);
untill time 150
i'm trying to do loop in embedded matrix function as below command:
function Xnew = stats(u,Mean, Std)
%#eml
for j=1:150,
Xnew = (u-Mean(1,j:j+2))./Std(1,j:j+2);
end
unfortunately i received this error,
"Could not determine the size of this expression"
I'm doing looping because i want to pick the submatrix that will be used in the equation.
What should i change above command so as i can get the result as i want? anybody have idea?
  1 个评论
Jan
Jan 2012-7-18
I have problems to determine the size of u also. Are u and Mean, Std and XNew different variables? Then please edit the question and brush up the formatting.
Does Matlab have a chance to know the size of u?
Is there a reason to overwrite XNew in each iteration of the for j loop?

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采纳的回答

Kaustubha Govind
Kaustubha Govind 2012-7-18
Strange. This works fine for me (I'm using R2011b). Perhaps you are using an older version of MATLAB? What about if you pre-allocate Xnew at the top of the function:
Xnew = zeros(1,3);
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yana osman
yana osman 2012-8-6
In my "from file" block does not have :data interpolation within time range" dialog. its only have "file name and "sample time". Any alternative step can i do to turn off linear interpolation? by the way i'm using MATLAB R2009a
Kaustubha Govind
Kaustubha Govind 2012-8-6
Yana: Sorry, perhaps the option to turn off interpolation was only introduced in a later release. You could try using Inport blocks to import data - these blocks should have an "Interpolate data" checkbox which you can turn off.

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更多回答（1 个）

Fred Smith
Fred Smith 2012-7-18
In more recent versions your code should just work. However, in older versions the size of this pattern was not understood:
j:j+2
Simply rewrite it as:
j + (0:2)
HTH,
Fred

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