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.

Answer 2

Solution in 2 steps using ddply ( i am not happy with , but I get the result)

dat <- ddply(df,.(Par1,Par2),function(x){
  data.frame(ParD=paste(paste(x$ParD),collapse='_'),
             Num.pre =length(x$Type[x$Type =='pre']),
             Num.post = length(x$Type[x$Type =='post']))
})

merge(dfw,dat)
 Par1 Par2 post pre        ParD Num.pre Num.post
1    A    D  2.0   1     foo_bar       1        1
2    B    E  4.0   3     baz_qux       1        1
3    C    F  6.5   5 bla_xyz_meh       1        2