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## Error: Inner matrix dimensions must agree.

Asked by Chien-Chia Huang

### Chien-Chia Huang (view profile)

on 15 Jun 2011
Accepted Answer by Paulo Silva

### Paulo Silva (view profile)

Hi, I am using "gamultiobj" to solve my problem. I, however, have no idea why the error message occurred

```??? Error using ==> mtimes
Inner matrix dimensions must agree.
```
```Error in ==> col_mop>@(x)x'*(B'*B)*x at 50
fun1 = @(x) x'*(B'*B)*x;
```

My objective function is coded as follows

```fun1 = @(x) x'*(B'*B)*x;
fun2 = @(x) x'*x;
bifun = @(x) [fun1(x) fun2(x)];
```

The dimension of B'*B is m so x is an m-by-1 vector. The syntax for gamultiobj is

```X = gamultiobj(FITNESSFCN,NVARS,A,b,Aeq,beq,LB,UB,options)
```

I have properly input the number of decision variables (NVARS) as m but the error message shows. I also check the dimensions using the command "whos" which showed what I wanted. Is there anything wrong?

Thanks in advance.

## 1 Answer

### Paulo Silva (view profile)

Answer by Paulo Silva

on 15 Jun 2011
Accepted answer

Matt Fig

### Matt Fig (view profile)

on 15 Jun 2011

@Chhien-Chia,

Show us the output of the following:

size(x) % I mean the argument to fun1 here...
size(B)

Chien-Chia Huang

### Chien-Chia Huang (view profile)

on 15 Jun 2011

Thanks a lot, Paulo! I just found out what the problem is. The x in gamultiobj is by default supposed to be a row vector, but I thought intuitively of x as a column vector. The problem was just solved.

Chien-Chia Huang

### Chien-Chia Huang (view profile)

on 16 Jun 2011

sorry Matt I did not see your reply. The output of size(B) was 5-by-10 and size(x) was 10-by-1. But the requested x in gamultiobj should be 1-by-10. Thanks, anyway. :D

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