[R] Matlab inv() and R solve() differences

[Peter Dalgaard]

Joseph P Gray wrote:
> I submit the following matrix to both MATLAB and R
> 
> x=  0.133 0.254 -0.214 0.116
>     0.254 0.623 -0.674 0.139
>    -0.214 -0.674 0.910 0.011
>     0.116 0.139  0.011 0.180
> 
> MATLAB's inv(x) provides the following
>  137.21 -50.68 -4.70 -46.42
> -120.71  27.28 -8.94 62.19
> -58.15   6.93  -7.89  36.94
>   8.35   11.17 10.42 -14.82
> 
> R's solve(x) provides:
> 261.94 116.22 150.92 -267.78
> 116.22 344.30 286.68 -358.30
> 150.92 286.68 252.96 -334.09
> -267.78 =358.30 -334.09 475.22
> 
> inv(x)*x = I(4)
> and solve(x)%*%x = I(4)
> 
> Is there a way to obtain the MATLAB result in R?

Multiply x[3,4] by 10:

 > xx <- x
 > xx[3,4]<-0.11
 > solve(xx)
            [,1]      [,2]      [,3]      [,4]
[1,]  137.20892 -50.67500 -4.705127 -46.41581
[2,] -120.71445  27.27570 -8.937571  62.19270
[3,]  -58.15073   6.93474 -7.886343  36.93919
[4,]    8.34851  11.17053 10.415928 -14.81602



-- 
    O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907