[R] threshold matrix

Alaios alaios at yahoo.com
Fri Apr 29 16:44:59 CEST 2011

```Thanks a lot.
I finally used

M2 <- M
M2[M < thresh] <- 0
M2[M >= thresh] <- 1

as I noticed that this one line

M2 <- as.numeric( M[] < thresh )
vectorizes my matrix.

One more question I have two matrices that only differ slightly. What will be the easiest way to compare and find the cells that are not the same?

Best Regards
Alex

--- On Fri, 4/29/11, David Winsemius <dwinsemius at comcast.net> wrote:

> From: David Winsemius <dwinsemius at comcast.net>
> Subject: Re: [R] threshold matrix
> To: "Alaios" <alaios at yahoo.com>
> Cc: R-help at r-project.org
> Date: Friday, April 29, 2011, 2:57 PM
>
> On Apr 29, 2011, at 9:37 AM, Alaios wrote:
>
> > Dear all,
> > I have a quite big matrix which I would like to
> threshold.
> > If the value is below threshold the cell should be
> zero
> > and
> > if the value is over threshold the cell should be one
>
> M2 <- M
> M2[M < thresh] <- 0
> M2[M >= thresh] <- 1
>
> or perhaps simply:
>
> M2 <- as.numeric( M[] < thresh )
> >
> > One really simple way to do that is two have a nested
> loop and check cell by cell.
> >
> > The problem is that this seems to be really time
> consuming and ineficient.
> >
> > What do you suggest me to try out?
>
> --
> David Winsemius, MD
> West Hartford, CT
>
>

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