[R] indexing a vector

Erin Hodgess hodgess at uhddx01.dt.uh.edu
Tue May 8 05:30:56 CEST 2001

Hi Jeff!

Try this:

which(mymatrix == 4, arr.ind=TRUE)

Hope this help!
Erin M. Hodgess, Ph.D.
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
One Main Street 
Houston, TX 77002
e-mail: hodgess at uhddx01.dt.uh.edu


Subject: Re: [R] indexing a vector
> > Dear R-List,
> >
> > How can one look up the row/column number for a given value in a matrix
> > data.frame?  For example in a matrix that contains only unique values
> > in [,1] how can I find value x in [,1] and report its row number?
> >
> match(x,matrix[,1])
> -thomas

    As a follow up to this question,  what's the easiest way to
    find the column and row indicies for a specified value in a matrix,
    when you don't know which column it's in (as assumed above)?

    So if   mymatrix <- matrix(c(3, 2, 4, 1), nrow = 2),  what's the easiet
    to see that the value 4 is in position (1, 2) ?

    Thanks much,

        Jeff Miller

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