Rebuild a complex dataset from long to wide using recast ()

Question

I am working with a dataset that comes with lme4, and I'm trying to learn how to use reshape2 to convert it from long to wide [full code at the end of the message].

library(lme4) data("VerbAgg") # load the dataset 

The data set has 9 variables; "Anger", "Sex" and "id" are not dependent on the "element", but "resp", 'btype', 'situ', 'mode' and 'r2' do.

I was able to successfully convert the data set from long to wide using the reshape () function:

 wide <- reshape(VerbAgg, timevar=c("item"), idvar=c("id", 'Gender', 'Anger'), dir="wide") 

Which gives 316 observations on 123 variables and is apparently correctly transformed. However, I had no success using reshape / reshape2 to play back a wide data frame.

 wide2 <- recast(VerbAgg, id + Gender + Anger ~ item + variable) Using Gender, item, resp, id, btype, situ, mode, r2 as id variables Error: Casting formula contains variables not found in molten data: Anger 

I cannot 100% understand how recast defines identification variables, but I am very confused why it does not see "Anger". Similarly

 wide3 <- recast(VerbAgg, id + Gender + Anger ~ item + variable, id.var = c("id", "Gender", "Anger")) Error: Casting formula contains variables not found in molten data: item 

Can anyone see what I'm doing wrong? I would like to get a better understanding of melt / casting!

Full code:

 ## load the lme4 package library(lme4) data("VerbAgg") head(VerbAgg) names(VerbAgg) # Using base reshape() wide <- reshape(VerbAgg, timevar=c("item"), idvar=c("id", 'Gender', 'Anger'), dir="wide") # Using recast library(reshape2) wide2 <- recast(VerbAgg, id + Gender + Anger ~ item + variable) wide3 <- recast(VerbAgg, id + Gender + Anger ~ item + variable, id.var = c("id", "Gender", "Anger")) # Using melt/cast m <- melt(VerbAgg, id=c("id", "Gender", "Anger")) wide <- o cast(m,id+Gender+Anger~...) Aggregation requires fun.aggregate: length used as default # Yields a list object with a length of 8? m <- melt(VerbAgg, id=c("id", "Gender", "Anger"), measure.vars = c(4,6,7,8,9)) wide <- dcast(m, id ~ variable) # Yields a data frame object with 6 variables. 

Answer 1

I think the following code does what you want.

 library(lme4) data("VerbAgg") # Using base reshape() wide <- reshape(VerbAgg, timevar=c("item"), idvar=c("id", 'Gender', 'Anger'), dir="wide") dim(wide) # 316 123 # Using melt/cast require(reshape2) m1 <- melt(VerbAgg, id=c("id", "Gender", "Anger","item"), measure=c('resp','btype','situ','mode','r2')) wide4 <- dcast(m1,id+Gender+Anger~item+variable) dim(wide4) # 316 123 R> wide[1:5,1:6] Anger Gender id resp.S1WantCurse btype.S1WantCurse situ.S1WantCurse 1 20 M 1 no curse other 2 11 M 2 no curse other 3 17 F 3 perhaps curse other 4 21 F 4 perhaps curse other 5 17 F 5 perhaps curse other R> wide4[1:5,1:6] id Gender Anger S1WantCurse_resp S1WantCurse_btype S1WantCurse_situ 1 1 M 20 no curse other 2 2 M 11 no curse other 3 3 F 17 perhaps curse other 4 4 F 21 perhaps curse other 5 5 F 17 perhaps curse other