Thank you, that really worked. Actually received an even shorter version:
rowSums((t(apply(D > 0, 1, cumsum)) <= 3) * D)
2013/5/21 Xiao He <praguewaterme...@gmail.com>
> 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.
>>>
>>
>>
>
[[alternative HTML version deleted]]
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