Question

I’m trying to change a data frame column (var3, in the example below) that has multiple values for factor levels of another variable (names, in the example below). I’d like var3 to be split into separate columns, one for each value, so that the factor levels in names do not repeat. My other variables (var1, var2) repeat where necessary to provide space for var3.

This is the kind of data I have:

df1 <- structure(list(name = structure(c(2L, 4L, 4L, 4L, 3L, 5L, 5L, 
1L), .Label = c("fifth", "first", "fourth", "second", "third"
), class = "factor"), var1 = c(90L, 84L, 84L, 84L, 18L, 22L, 
22L, 36L), var2 = c(301L, 336L, 336L, 336L, 412L, 296L, 296L, 
357L), var3 = c(-0.582075925, -1.108889624, -1.014962009, -0.162309524, 
-0.282309524, 0.563055819, -0.232075925, -0.773353424)), .Names = c("name", 
"var1", "var2", "var3"), class = "data.frame", row.names = c(NA, -8L))

This is what i’d like:

df2 <- structure(list(name = structure(c(2L, 4L, 3L, 5L, 1L), .Label = c("fifth", 
"first", "fourth", "second", "third"), class = "factor"), var1 = c(90L, 
84L, 18L, 22L, 36L), var2 = c(301L, 336L, 412L, 296L, 357L), 
var3 = c(-0.582075925, -1.108889624, -0.282309524, 0.563055819, 
-0.773353424), var3.2 = c(NA, -1.014962009, NA, -0.232075925, 
NA), var3.3 = c(NA, -0.162309524, NA, NA, NA)), .Names = c("name", "var1", 
"var2", "var3", "var3.2", "var3.3"), class = "data.frame", row.names = c(NA, -5L))

I’ve looked at reshape and ddply, but can’t get them to give me this output.

Answer 1

Here’s a base solution:

> df1$seqnam <- ave(as.character(df1$name), df1$name, FUN=seq)  # creates a "time" index 
> reshape(df1, direction="wide", timevar="seqnam",  idvar=c("name", "var1", "var2") )
    name var1 var2     var3.1     var3.2     var3.3
1  first   90  301 -0.5820759         NA         NA
2 second   84  336 -1.1088896 -1.0149620 -0.1623095
5 fourth   18  412 -0.2823095         NA         NA
6  third   22  296  0.5630558 -0.2320759         NA
8  fifth   36  357 -0.7733534         NA         NA