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I am working on matrix operations in R. I came across 2 different methods to find inverse of a matrix namely:

  • MASS::ginv(a)
  • solve(a)

They returns the same result or so it seems but when I try to equate them using ginv(a) == solve(a) only elements of leading diagonal seem to be equal. It returns True for those elements otherwise it returns zero.

I am perplexed with this behavior. This is happening even though I can see that they have exactly same numerical values.

I am working on R Studio and Windows.

 library(MASS)
 a1 <- rbind(c(1,-0.25),c(-0.25,1))
 solve(a1)
 ginv(a1)
 solve(a1) == ginv(a1)

Please somebody explain to me what is happening. Is it because of pseudo inverse?

Andrie
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Abhishek Sharma
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