Error with matrix multiplication?

I have two matrices I'd like to multiply. Matrix A has dimensions 107x817. Matrix B has dimensions 817x1. My understanding of matrix multiplication is that the inner dimensions have to agree. So if I multiply A*B than it should work? However, I keep getting back an error.

Answer 1

[Matt J]

Yep, it should work, as the following example shows. I would check to make sure the matrix dimensions are really what you think they are.

A=rand(107,817); B=rand(817,1);

C=A*B;

whos A B C

  Name        Size              Bytes  Class     Attributes

  A         107x817            699352  double              
  B         817x1                6536  double              
  C         107x1                 856  double              

Answer 2

[Jan]

This should work. Use the debugger to let Matlab stop when the error occurs - type this in the command window:

dbstop if error

Then run your code again. If Matlab stops, check if the sizes of the arrays are what you expect them to be.