[R] data frame transformation

[Andras Farkas]

Hello Everyone,

would you be able to assist with some expertise on how to get the following done in a way that can be applied to a data set with different dimensions and without all the line items here?

we have:

id<-c(1,1,1,2,2,2,2,3,3,4,4,4,4,5,5,5,5)#length of unique IDs may differ of course in real data set, usually in magnitude of 10000
letter<-c(sample(c("A","B","C","D","E"),3),sample(c("A","B","C","D","E"),4),sample(c("A","B","C","D","E"),2),
          sample(c("A","B","C","D","E"),4),sample(c("A","B","C","D","E"),4))#number of unique "letters" is less than 4000 in real data set and they are no duplicates within same ID
weight<-c(sample(c(1:30),3),sample(c(1:30),4),sample(c(1:30),2),
          sample(c(1:30),4),sample(c(1:30),4))#number of unique weights is below 50 in real data set and they are no duplicates within same ID


data<-data.frame(id=id,letter=letter,weight=weight)

#goal is to get the following transformation where a column is added for each unique letter and the weight is pulled into the column if the letter exist within the ID, otherwise NA
#so we would get datatransform like below but without the many steps described here

datatransfer<-data.frame(data,apply(data[2],2,function(x) ifelse(x=="A",data$weight,NA)))
datatransfer<-data.frame(datatransfer,apply(datatransfer[2],2,function(x) ifelse(x=="B",data$weight,NA)))
datatransfer<-data.frame(datatransfer,apply(datatransfer[2],2,function(x) ifelse(x=="C",data$weight,NA)))
datatransfer<-data.frame(datatransfer,apply(datatransfer[2],2,function(x) ifelse(x=="D",data$weight,NA)))
datatransfer<-data.frame(datatransfer,apply(datatransfer[2],2,function(x) ifelse(x=="E",data$weight,NA)))

colnames(datatransfer)<-c("id","weight","letter","A","B","C","D","E")
much appreciate the help,

thanks

Andras