Matrix Inversion

I got the following error:

a = read.csv("mat.csv")
b = as.matrix(a)
tb = t(b)
bb = tb %*% b
dim(bb)
ibb = solve(bb)
bb %*% ibb

  

ibb = solve(bb)
    

Error in solve.default(bb) :
  system is computationally singular: reciprocal condition number =
1.77573e-19
  
Are there any ways to find more information about why it is singular?

Thanks.
  

Yes. Since the matrix is positive semidefinite by construction, I'd
probably go for chol(bb, pivot=TRUE), then the first "rank" elements of
"pivot" gives you a maximal subset of linearly independent columns, and
you can proceed by something like lm(b[,-subset]~b[,subset]) to see what
the linear dependencies are.

(Other approaches could be eigen() and svd().)

O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
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