R help - Jul 2010 - replace negative numbers by smallest positive value in matrix

Hi Group,

I have a matrix, and I would like to replace numbers less than 0 by
the smallest minimum number. Below is an
small matrix, and the loop I used. I would like to get suggestions on
the "R way" to do this.

Thanks,

Juliet

# example data set

mymat <- structure(c(-0.503183609420937, 0.179063475173256,
0.130473004669938,
-1.80825226960127, -0.794910626384209, 1.03857280868547, 0.362120146065799,
-2.01124119488992, -1.49083525457822, -0.356354715035589, -0.306686279071398,
0.0789120002882668, 1.50314029609087, -0.0177677865019544, 1.31642572649823,
1.78842032090131, -0.991393884836917, -0.868946528068323, -0.325472385456867,
0.119383948888965), .Dim = c(5L, 4L))


# replacement of negative numbers

for (mycol in 1:ncol(mymat)) {
   sort_dat <- sort(mymat[,mycol])
   min_pos_index <- min(which(sort_dat >0 ))
   min_pos_val <- sort_dat[min_pos_index]
   neg_nums <- which(mymat[,mycol]  <= 0)
   mymat[neg_nums,mycol] <- min_pos_val
}

Hi, Juliet,

Something like this?

mymat[mymat<0]<-min(mymat[mymat>0])

Jun

On Thu, Jul 15, 2010 at 10:55 AM, Juliet Hannah <juliet.hannah at
gmail.com> wrote:
> Hi Group,
>
> I have a matrix, and I would like to replace numbers less than 0 by
> the smallest minimum number. Below is an
> small matrix, and the loop I used. I would like to get suggestions on
> the "R way" to do this.
>
> Thanks,
>
> Juliet
>
> # example data set
>
> mymat <- structure(c(-0.503183609420937, 0.179063475173256,
0.130473004669938,
> -1.80825226960127, -0.794910626384209, 1.03857280868547, 0.362120146065799,
> -2.01124119488992, -1.49083525457822, -0.356354715035589,
-0.306686279071398,
> 0.0789120002882668, 1.50314029609087, -0.0177677865019544,
1.31642572649823,
> 1.78842032090131, -0.991393884836917, -0.868946528068323,
-0.325472385456867,
> 0.119383948888965), .Dim = c(5L, 4L))
>
>
> # replacement of negative numbers
>
> for (mycol in 1:ncol(mymat)) {
> ? sort_dat <- sort(mymat[,mycol])
> ? min_pos_index <- min(which(sort_dat >0 ))
> ? min_pos_val <- sort_dat[min_pos_index]
> ? neg_nums <- which(mymat[,mycol] ?<= 0)
> ? mymat[neg_nums,mycol] <- min_pos_val
> }
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>

Juliet -
    Since you're operating on each column, apply() would
be the appropriate function;

mymat = apply(mymat,2,function(x){x[x<0] = min(x[x>0]);x})


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Thu, 15 Jul 2010, Juliet Hannah wrote:
> Hi Group,
>
> I have a matrix, and I would like to replace numbers less than 0 by
> the smallest minimum number. Below is an
> small matrix, and the loop I used. I would like to get suggestions on
> the "R way" to do this.
>
> Thanks,
>
> Juliet
>
> # example data set
>
> mymat <- structure(c(-0.503183609420937, 0.179063475173256,
0.130473004669938,
> -1.80825226960127, -0.794910626384209, 1.03857280868547, 0.362120146065799,
> -2.01124119488992, -1.49083525457822, -0.356354715035589,
-0.306686279071398,
> 0.0789120002882668, 1.50314029609087, -0.0177677865019544,
1.31642572649823,
> 1.78842032090131, -0.991393884836917, -0.868946528068323,
-0.325472385456867,
> 0.119383948888965), .Dim = c(5L, 4L))
>
>
> # replacement of negative numbers
>
> for (mycol in 1:ncol(mymat)) {
>   sort_dat <- sort(mymat[,mycol])
>   min_pos_index <- min(which(sort_dat >0 ))
>   min_pos_val <- sort_dat[min_pos_index]
>   neg_nums <- which(mymat[,mycol]  <= 0)
>   mymat[neg_nums,mycol] <- min_pos_val
> }
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.
>