reshape2

This question already has an answer here: Reshaping multiple sets of measurement columns (wide format) into single columns (long format) 7 answers I have an R dataframe that I scraped from the internet using readHTMLTable() in the XML package. The table looks like the following excerpt with multiple variables/columns for population and year. (Note that the years are not duplicated across columns and represent a unique identifier for population.) year1 pop1 year2 pop2 year3 pop3 1 2 16XX 4675,0 1900 6453,0 1930 9981,2 3 17XX 4739,3 1901 6553,5 1931 ... 4 17XX 4834,0 1902 6684,0 1932 5 180X 4930

I have what should be a simple reshaping problem, but I can't figure it out. Part of my data looks like this: foo <- structure(list(grade = c(3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 3, 3, 4, 4, 5, 5, 6, 6), var.type = structure(c(3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L, 3L, 2L ), .Label = c("Raw Score", "SE", "SS"), class = "factor"), var.val = c(120L, 47L, 120L, 46L, 120L, 46L, 120L, 47L, 120L, 46L, 120L, 46L, 120L, 12L, 120L, 14L, 120L, 16L, 120L, 20L)), .Names = c("grade", "var.type", "var.val"), row.names = c(2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L,

This question already has an answer here: can the value.var in dcast be a list or have multiple value variables? 3 answers Convert data from long format to wide format with multiple measure columns 4 answers Here is toy data set for this example: data <- data.frame(x=rep(c("red","blue","green"),each=4), y=rep(letters[1:4],3), value.1 = 1:12, value.2 = 13:24) x y value.1 value.2 1 red a 1 13 2 red b 2 14 3 red c 3 15 4 red d 4 16 5 blue a 5 17 6 blue b 6 18 7 blue c 7 19 8 blue d 8 20 9 green a 9 21 10 green b 10 22 11 green c 11 23 12 green d 12 24 How can I cast or spread variable y, to

In the help files for dcast.data.table , there is a note stating that a new feature has been implemented: "dcast.data.table allows value.var column to be of type list" I take this to mean that one can have multiple value variables within a list, i.e. in this format: dcast.data.table(dt, x1~x2, value.var=list('var1','var2','var3')) But we get an error: 'value.var' must be a character vector of length 1. Is there such a feature, and if not, what would be other one-liner alternatives? EDIT: In reply to the comments below There are situations where you have multiple variables that you want to

Edit -- This question was originally titled << Long to wide data reshaping in R >> I'm just learning R and trying to find ways to apply it to help out others in my life. As a test case, I'm working on reshaping some data, and I'm having trouble following the examples I've found online. What I'm starting with looks like this: ID Obs 1 Obs 2 Obs 3 1 43 48 37 1 27 29 22 1 36 32 40 2 33 38 36 2 29 32 27 2 32 31 35 2 25 28 24 3 45 47 42 3 38 40 36 And what I want to end up with will look like this: ID Obs 1 mean Obs 1 std dev Obs 2 mean Obs 2 std dev 1 x x x x 2 x x x x 3 x x x x And so forth. What