Complicated reshaping

Question

I want to reshape my dataframe from long to wide format and I loose some data that I\'d like to keep. For the following example:

df <- data.frame(Par1 =          


        

Answer 1

One Step solution combining reshape::cast with plyr::ddply

cast(Par1 + Par2 + ParD ~ Type, data = ddply(df, .(Par1, Par2), transform, 
  ParD = paste(ParD, collapse = "_")), fun  = c(mean, length))

NOTE that the dcast function in reshape2 does not allow multiple aggregate functions to be passed, while the cast function in reshape does.