R : Finding the ordering index vector

The ordering index vector is a vector that contains indices of another vector.  It’s basically the other vector, but ordered (decreasing or increasing).  Instead of having the values it has the indices :)  I spent close to an hour to find this line :) And here it is.  In all its glory :)

sort.int(VECTOR, index.return=TRUE)

The result of this command is a bit strange (for me).  It returns an object that contains the ordered vector and the ordered index vector in a list.  Long story short, I can’t access them like I would want to.  So the command I ended up using is a bit more complex:

unlist(as.matrix(sort.int(VECTOR, index.return=TRUE))[2])

Notice that I coerce the resulting list into a matrix.  This results in a matrix containing two elements: [1]->ordered vector and [2]->  ordered index vector. Therefore I chose the second element in the returned list and unlisted it into a vector.  This is what I wanted as I can index a vector :)


About joelgranados

I'm fascinated with how technology and science impact our reality and am drawn to leverage them in order to increase the potential of human activity.
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3 Responses to R : Finding the ordering index vector

  1. Kulvait says:

    sort.int(VECTOR, index.return=TRUE)$ix is the way where to go.

  2. W.F says:

    Wouldn’t using order(VECTOR) do the trick? it returns a vector and is easy to use :)

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