Error using inv Matrix must be square

So im pretty new to mathlab can someone just guide me and tell me what i am missing?

B =

   0.0000 - 7.5700i   0.0000 + 3.3300i   0.0000 + 0.0000i   0.0000 + 3.3300i   0.0000 - 1.3600i
   0.0000 + 3.3300i   0.0000 -16.6600i   0.0000 + 3.3300i   0.0000 +10.0000i   0.0000 + 0.0000i
   0.0000 + 0.0000i   0.0000 + 3.3300i   0.0000 - 7.7100i   0.0000 + 3.3300i   0.4100 - 1.5200i
   0.0000 + 3.3300i   0.0000 +10.0000i   0.0000 + 3.3300i -17.6600 + 0.0000i  -0.9000 - 1.2000i

>> inv(B) Error using inv Matrix must be square.

Answer 1

[Stephen23]

Lets have a look at the size of this matrix:

>> B = [0-7.57i, 0+3.33i,  0+0.00i,   0+3.33i,   0-1.36i;...
        0+3.33i, 0-16.66i, 0+3.33i,   0+10.i,    0.00+0.i;...
        0+0.00i, 0+3.33i,  0-7.71i,   0+3.33i,   0.41-1.52i;...
        0+3.33i, 0+10.i,   0+3.33i, -17.66+0.i, -0.90-1.20i];
>> size(B)
ans =
   4     5

So the matrix is clearly not square. And yet the matrix inverse operation is only defined for square matrices: "inv(X) returns the inverse of the square matrix X" states the documentation clearly.

Every source you will care to look at will tell you that a matrix must be square to be invertable: "In linear algebra, an n-by-n square matrix A is called invertible..."

[Marvin Castellanos]

so what can i do to get the inv matrix of a 4x5?

[Torsten]

Maybe you mean

A=pinv(B)

?

Best wishes

Torsten.

[Stephen23]

@Marvin Castellanos: when you can tell us what the inverse of a non-square matrix is, then we will show you how to code it.

There are some situations where a left / right inverse might be possible: "Non-square matrices (m-by-n matrices for which m ≠ n) do not have an inverse. However, in some cases such a matrix may have a left inverse or right inverse. If A is m-by-n and the rank of A is equal to n, then A has a left inverse: an n-by-m matrix B such that BA = I. If A has rank m, then it has a right inverse: an n-by-m matrix B such that AB = I."

Quoted from

http://en.wikipedia.org/wiki/Invertible_matrix

But then you will need to tell us more about your matrix before we can tell you if this is possible.