[R] replace negative numbers by smallest positive value in matrix

[Juliet Hannah]

Thanks Jun and Phil!


On Thu, Jul 15, 2010 at 12:16 PM, Phil Spector
<spector at stat.berkeley.edu> wrote:
> 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
>> }
>>
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>>
>