Oops, a couple of missing brackets in the previous reply:
foo<-function(x){
temp=x[x>0]
if(length(temp)>=3) sum(temp[1:3])
else sum(temp)
} #<----This was missing in the previous post
set.seed(2)
mat<-matrix(sample(0:4, 25, replace=T, prob=c(1/2,rep(1/8,4))), ncol=5)
#add a right parenthesis.
mat
On Tue, May 21, 2013 at 3:47 AM, Xiao He <praguewaterme...@gmail.com> wrote:
> Does this work? Probably not the fastest, but I think it does the job.
>
> foo<-function(x){
> temp=x[x>0]
> if(length(temp)>=3) sum(temp[1:3])
> else sum(temp)
>
> set.seed(2)
> mat<-matrix(sample(0:4, 25, replace=T, prob=c(1/2,rep(1/8,4)), ncol=5)
> mat
>
> # [,1] [,2] [,3] [,4] [,5]
> #[1,] 0 1 2 4 3
> #[2,] 3 0 0 1 0
> #[3,] 2 4 4 0 4
> #[4,] 0 0 0 0 0
> #[5,] 1 2 0 0 0
>
>
> apply(mat, 1, foo) #Apply the function to each row of the matrix
> #[1] 7 4 10 0 3
>
>
>
> On Tue, May 21, 2013 at 2:16 AM, José Verhoeven <j...@memo2.nl> wrote:
>
>> Hi there,
>> I've got this matrix D with, say 10 rows and 20 columns. For each row I
>> want
>> to sum the first 3 non zero elements and put them in a vector z.
>>
>> So if the first row D[1,] is
>> 0 3 5 0 8 9 3 2 4 0
>>
>> then I want z
>> z<-D[1,2]+D[1,3]+D[1,5]
>>
>> But if there are less than 3 non zero elements, those should be summed. If
>> there are no non zero elements, the result must be zero.
>>
>> So if the first row D[1,] is
>> 0 0 3 0 1 0 0 0 0 0
>>
>> then I want z
>> z<-D[1,3]+D[1,5]
>>
>> Hope someone can help me out!
>>
>> [[alternative HTML version deleted]]
>>
>> ______________________________________________
>> R-help@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.
>>
>
>
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