[R] get the values of unique ID

[Spencer Graves]

tst.df <- data.frame(ID=rep(1:2, 2), Values=1:4)
tapply(tst.df$Values, tst.df$ID, mean)
tapply(tst.df$Values, tst.df$ID, sd)

Is this what you want?
(Time it using "start.time <- proc.time()" before and "elapsed.time <- 
proc.time()-start.time" after.)
Spencer Graves

Jane Yu wrote:
> Hi, All,
> I wonder anyone can help me find a faster algorithm to
> get the values of unique ID (most ID has 2-3 values,
> varies).
> My data looks like:
> ID Values
> 1 250
> 2 300
> 1 251
> 3 5000
> 4 600
> 10 521
> 3  5500
> I would like output to look like:
> ID, avg(values), stdev(values), value 1,val 2,val3,...
> 
> I used 2 for loops trying to get the values
> for (i in 1:n){
>   value <- NULL
>   for(j in 1:m){
>     if(data[j,1] == uniqueid[i]){
>          value <- c(value, data[j,2])
>           ....
>     }
>   }
> }
> Since both n and m are about 10000, the algorithm is
> really slow.  I believe there is some function out
> there that can do better than this in R. 
> 
> Thanks
> 
> -Jindan
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help