[R] distributing the values of data frame to a vector based on......
jim holtman
jholtman at gmail.com
Tue Oct 23 19:09:59 CEST 2007
Does this do what you want? Another way of doing matrix addressing:
> dat[cbind(year,region)]
[1] 1 5 9 10 18 3 4 8 16 17 2 6 7 15 19
On 10/23/07, Daniel O'Shea <dan.oshea at dnr.state.mn.us> wrote:
> I am trying to distribute the entries of a data frame (dat) to a vector (water) based on the values of two other vectors (region and year). region is also the columns and year the rows of the data frame (dat). I can write a bunch of ifelse statements or I created the for statement below - but there must be a simpler way?? The for statement probably won't work if I am distributing a non numeric factor. Is there a built in function that does this?
>
> Dan O'Shea
>
>
> ##example data
> dat<-matrix(c(1,2,3,4,5,6,7,8,9,10,15,16,17,18,19),nrow=3,ncol=5)
> colnames(dat)<-1:5
> rownames(dat)<-1:3
> region<-rep(1:5,3)
> year<-rep(1:3,5)
>
>
> ####distributes the data frame values based on column and row identity, but
> ###then must perform the apply statement to create a single vector.
> water<-vector()
> for(i in 1:5){
> for(j in 1:3){
> water.b<-ifelse(region==region[i]&year==year[j],dat[j,i],0)
> water<-cbind(water,water.b)
> }}
> waterlevel<-apply(water,1,sum)
>
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> and provide commented, minimal, self-contained, reproducible code.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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