Can anyone please tell me why I am getting this error?

A =

     2     4     1
     3     1     4
     5     6     0

>> A=finverse(A) Undefined function 'finverse' for input arguments of type 'double'.

>>

Answer 1

[Star Strider]

The finverse function is in the Symbolic Math Toolbox, and creates the inverse of a symbolic function.

You likely want the inv function for your matrix. If you are doing matrix calculations, it is preferable to use the mldivide function, or more directly the (\) (backslant) operator (if possible in your calculations).

[Star Strider]

The easiest way to invert your matrix then is simply to use inv. If you want to use the Symbolic Math Toolbox, declare your A matrix as a symbolic object first:

syms A

A = [2     4     1
     3     1     4
     5     6     0]

Ainv = inv(A)

It will still be a double data type, so there is no advantage to doing it as a symbolic object.

[Christopher Creutzig]

Your sequence of commands does not create a symbolic matrix. The assignment to A discards the previous symbolic variable A.

A = sym([2     4     1
         3     1     4
         5     6     0])
inv(A)

ans =

[ -8/15, 2/15,  1/3]
[   4/9, -1/9, -1/9]
[ 13/45, 8/45, -2/9]

[Star Strider]

@Christopher — Noted. You’re correct.

Answer 2

[Image Analyst]

finverse() is not in base MATLAB. Do you think it is suppose to be in one of your toolboxes? If so, which one? List in in the products drops down list below this comment. Or is it a custom function you wrote but did not include here?

[Iain]

Or, is it just a typo?

[Andrew Reibold]

Symbolic Math Toolbox

Answer 3

[Segun]

Thanks Star Strider & image analyst. I am just interested in creating the inverse of the matrix. The Symbolic toolbox is included. I checked using vers cmd.

[Segun]

Thanks. prob solved.