Dear R gurus,
I'm trying to solve what I assume is a fairly simple problem, but I'm having
trouble finding the proper approach. I have a matrix where each column is some
object (e.g. a car) and each row is a numeric measurement of a feature of said
object (e.g. horse power, top speed, etc.). Let's also suppose that I know what
make the car is (e.g. toyota, ford, etc.), stored in a separate vector. What I
want to do is apply a custom function over each column of this matrix, but the
function will behave differently depending on the make of the car, so each time
a column is passed into my custom function, the function needs to know the make
of the car. What I imagine being able to do is something like this:
carmake<-c("Toyota","Ford","Chevy")
x<-matrix(1:12,nrow=4)
colnames(x)<-c("Car1","Car2","Car3")
rownames(x)<-c("Horsepower","TopSpeed","Weight","Cost")
res<-apply(my_matrix,2,my_func,carmake)
The obvious problem with this is that I cannot know which column 'my_func' is
working on, in order to know which column to get the car make from. I then
thought I could try and match on column name, but when the column is passed
into 'my_func' it loses the column name.
Anyway, I hope that made sense. I appreciate any help you may offer!
Mark T. W. Ebbert
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