[R] How to avoid two for loops?

[Ivan Calandra]

Hi Tammy,

I think you're looking for aggregate() or something similar (from 
package plyr for example).

Something along those lines:
aggregate(DisplaySize~Brand, data=cl, FUN=sum)

HTH,
Ivan

--
Ivan Calandra, ATER
University of Reims Champagne-Ardenne
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ivan.calandra at univ-reims.fr
https://www.researchgate.net/profile/Ivan_Calandra

Le 25/02/15 10:08, conglan a écrit :
> HI,
>
> I have the following large data set:
> the sample is as the following:
>    Country  Product   Brand  Year_Month   DisplaySize   OperationSystem
>       AE         1           20    201204              1                  1
>       AE         5           20    201204              1                  1
>       AE         2           28    201204              3                  2
>       AE         3           27    201204              1                  1
>       AE         1           20    201205              1                  1
>       AE         2           28    201205              3                  2
>       AE         4           20    201205              1                  2
>
> I want to calculate the extra three columns as the following:
> Let's say "20" is own brand
>   #The sums of display size produced by competing brand
>   #The sums of display size of other products produced by own brand
>   #The sums of display size of products of competing firm in the same
> operating system
>
> I build up the following codes, apprently two loop takes too long time:
>
> dd<-unique(cl$Year_Month)
>
> fldata<-data.frame(NULL)
>
> for ( i in 1:length(dd)){
>
>    cls<-cl[cl$Year_Month==dd[i],]
>    ws<-numeric(0)  #The sums of characteristics of products produced by
> competing firms
>    ws1<-numeric(0)  #The sums of characteristics of other products produced
> by firm
>    ws2<-numeric(0) #The sums of characteristics of products of competing
> firm in the same operating system
>
>
>    for (j in 1:dim(cls)[1]){
>
>     wd<-sum(cls[cls$Brand!=cls$Brand[j],]$DISPLAY_SIZE_INCH)
>     ws[j]<-wd
>     wc<-sum(cls[cls$Brand==cls$Brand[j] & cls$Item_Id!=cls$Item_Id[j]
> ,]$DISPLAY_SIZE_INCH)
>     ws1[j]<-wc
>     wf<-sum(cls[cls$Brand!=cls$Brand[j] &
> cls$OPERATING_SYST==cls$OPERATING_SYST[j]
> ,]$DISPLAY_SIZE_INCH)
>     ws2[j]<-wf
>     }
>
>    cls<-cbind(cls,SumPCf=ws,SumOPf=ws1,SumPCfOp=ws2)
>    fldata<-rbind(fldata,cls)
>
> }
>
>
> how can I avoid two loops and improve the speed of my code??????? any other
> solution?
>
>
> Thanks.
>
> Tammy
>
>
>
>
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