Matrix Inverse Code(c, c++, fortran or tksolver)

Question

I need a code to determine the inverse of an nxn matrix A using row operations. I am having a ridiculous time writing this code. Anything helps, I am a grad student and havent taken a programming class in years. Thanks.

Answer 1

You might not really want the inverse. If you're trying to solve a system of equations you'd be better off using LU decomposition.

You don't say what language you'd like to write this app in. Java has Apache Commons Math; Python has NumPy; FORTRAN has LinPack. Pick a language and use a library; don't write it yourself.

Answer 2

  SUBROUTINE MATINV(A,N)
  DIMENSION A(N,N)
  DO 1 I=1,N
     Z=A(I,I)
     A(I,I)=1.0
     DO 2 J=1,N
2       A(I,J)=A(1,J)/Z
     DO 1 K=1,N
        IF (K-I) 3,1,3
3          Z=A(K,I)
        A(K,I)=0.0
        DO 4 J=1,N
4          A(K,J)=A(K,J)-Z*A(I,J)
1 CONTINUE
  RETURN
  END

Answer 3

I suggest Scilab or MATLAB for matrix operations if you haven't taken a programming class in years.

If it is a one time calculation, look at WolframAlpha.

If using libraries is an option for C++, look at Armadillo.

Answer 4

Look at Numerical Recipies Online. The Fortran 77, Ansi C and Fortran 90 code is free and you can get pleanty of clues on how to best proceed.