I have a data.frame
consisting of numeric and factor variables as seen below.
testFrame <- data.frame(First=sample(1:10, 20, replace=T),
Second=sample(1:20, 20, replace=T), Third=sample(1:10, 20, replace=T),
Fourth=rep(c("Alice","Bob","Charlie","David"), 5),
Fifth=rep(c("Edward","Frank","Georgia","Hank","Isaac"),4))
I want to build out a matrix
that assigns dummy variables to the factor and leaves the numeric variables alone.
model.matrix(~ First + Second + Third + Fourth + Fifth, data=testFrame)
As expected when running lm
this leaves out one level of each factor as the reference level. However, I want to build out a matrix
with a dummy/indicator variable for every level of all the factors. I am building this matrix for glmnet
so I am not worried about multicollinearity.
Is there a way to have model.matrix
create the dummy for every level of the factor?
(Trying to redeem myself...) In response to Jared's comment on @Fabians answer about automating it, note that all you need to supply is a named list of contrast matrices. contrasts()
takes a vector/factor and produces the contrasts matrix from it. For this then we can use lapply()
to run contrasts()
on each factor in our data set, e.g. for the testFrame
example provided:
> lapply(testFrame[,4:5], contrasts, contrasts = FALSE)
$Fourth
Alice Bob Charlie David
Alice 1 0 0 0
Bob 0 1 0 0
Charlie 0 0 1 0
David 0 0 0 1
$Fifth
Edward Frank Georgia Hank Isaac
Edward 1 0 0 0 0
Frank 0 1 0 0 0
Georgia 0 0 1 0 0
Hank 0 0 0 1 0
Isaac 0 0 0 0 1
Which slots nicely into @fabians answer:
model.matrix(~ ., data=testFrame,
contrasts.arg = lapply(testFrame[,4:5], contrasts, contrasts=FALSE))