[R] how to extract specific subscript of a matrix

[Jeff Newmiller]

M <- matrix(c(2,2,rep(1,12), 2), nrow = 5,byrow = FALSE)
ix <- expand.grid( r = seq.int( nrow( M ) )
                 , c = seq.int( ncol( M ) )
                 )
ix[ 1 == c(M), ]


On June 10, 2020 5:29:10 PM PDT, Jinsong Zhao <jszhao using yeah.net> wrote:
>Hi there,
>
>I have a matrix similar as:
>
>M <- matrix(c(2,2,rep(1,12), 2), nrow = 5,byrow = FALSE)
>
>I hope to get the border subscript of the block with value 1. In the 
>above example, I hope to get:
>
>(3,1), (5,1), (5,2), (4,2), (4,3), (1,3), (1,2), (3,2)
>
>Is there any function can do that? or any implement idea? Thanks!
>
>Best,
>Jinsong
>
>______________________________________________
>R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

-- 
Sent from my phone. Please excuse my brevity.