Reshaping wide to long data.frames

wide2long.R

## transform an arbitrary 'wide' data.frame into a 'long' data.frame.

# load packages
library(reshape)


# sample wide data.frame
wide.df <- data.frame(Code = c("PPP001","PPP002"),
                      Country = c("ESP","FRA"), January2012 = c(110,50), February2012 = c(40,55),
                      March2012 = c(56,32))


## Flags
n.fixed.vars <-2 # how many vars you want to leave 'fixed'
v.names <- "Sales" # names of your time-varying variable
idvar <- names(long.df)[seq(n.fixed.vars)] # names of your fixed variables
timevar <- "Month" # name of the frequency of variation



long.df <- reshape(wide.df,
                   direction="long",
                   varying=list(names(long.df)[(n.fixed.vars+1):ncol(long.df)]),
                   v.names=v.names, 
                   idvar=idvar,
                   timevar=timevar,
                   times=names(long.df)[(n.fixed.vars+1):ncol(long.df)])
                   
rownames(long.df) <- NULL