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Index exceeds matrix dimensions.

Asked by Sara

Sara (view profile)

on 20 Jun 2012

for the code below I received the error index exceeds.. I do not know how can I fix it.

x = zeros( 2,length(v0) ) ;  
for k = 1:length(v0)
  A = [ factor1(:,k) factor2(:,k)];
  b = -rhs(:,k);
  x(:,k) = A\b ;
//end of for     

length v0 = 2501

A\b is 2 by 2 matrix but x(:,k) is 2 by 2501.

3 Comments

Walter Roberson

Walter Roberson (view profile)

on 20 Jun 2012

Which line is generating the error?

What are the sizes of factor1 and factor2 and rhs ?

Sara

Sara (view profile)

on 20 Jun 2012

the sizes of factor1 and factor2 are 2 by 2501.
by the line x (:,k) = A\b , it has error.

Walter Roberson

Walter Roberson (view profile)

on 20 Jun 2012

That doesn't sound like an "index exceeds" error, that sounds like an error about RHS having more non-singleton dimensions than the LHS has.

Please show the exact error.

If A\b is a 2 x 2 matrix, then were you only expecting a 2 x 1 matrix as the result of the A\b operation? Or you only care about one of the rows or one of the columns? Or you want to store all 4 results and do that in a single column ?

Sara

Sara (view profile)

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1 Answer

Answer by per isakson

per isakson (view profile)

on 20 Jun 2012

Do you use the debugger?

  1. Put a break on the line that causes the error or
  2. Tools | Debug | Stop if Error
  3. Run the code
  4. At the break inspect the values of the index

2 Comments

Walter Roberson

Walter Roberson (view profile)

on 20 Jun 2012

A zero index would generate the error about indices needing to be positive integers, not the error about exceeding matrix dimensions.

per isakson

per isakson (view profile)

on 20 Jun 2012

Thanks Walter; fixed. I try to make the point that better asking the debugger than Answer.

per isakson

per isakson (view profile)

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