Wrapping base R reshape for ease-of-use

Question

It is a truth universally acknowledged that R\'s base reshape command is speedy and powerful but has miserable syntax. I have therefore written a quick wrapper around it wh

Answer 1

I would also like to see an option to order the output, since that's one of the things I don't like about reshape in base R. As an example, let's use the Stata Learning Module: Reshaping data wide to long, which you are already familiar with. The example I'm looking at is the "kids height and weight at age 1 and age 2" example.

Here's what I normally do with reshape():

# library(foreign)
kidshtwt = read.dta("http://www.ats.ucla.edu/stat/stata/modules/kidshtwt.dta")
kidshtwt.l = reshape(kidshtwt, direction="long", idvar=1:2, 
                     varying=3:6, sep="", timevar="age")
# The reshaped data is correct, just not in the order I want it
# so I always have to do another step like this
kidshtwt.l = kidshtwt.l[order(kidshtwt.l$famid, kidshtwt.l$birth),]

Since this is an annoying step that I always have to go through when reshaping the data, I think it would be useful to add that into your function.

I also suggest at least having an option for doing the same thing with the final column order for reshaping from long to wide.

Example function for column ordering

I'm not sure of the best way to integrate this into your function, but I put this together to sort a data frame based on basic patterns for the variable names.

col.name.sort = function(data, patterns) {
  a = names(data)
  b = length(patterns)

  subs = vector("list", b)

  for (i in 1:b) {
    subs[[i]] = sort(grep(patterns[i], a, value=T))
    }
  x = unlist(subs)
  data[ , x ]
}

It can be used in the following manner. Imagine we had saved the output of your reshapeasy long to wide example as a data frame named a, and we wanted it ordered by "surveyNum", "caremgmt" (1-3), "prev" (1-3), "pio" (1-3), and "price" (1-3), we could use:

col.name.sort(a, c("sur", "car", "pre", "pio", "pri"))