Am 08.05.2010 15:43, schrieb Joris Meys:
Dear all,
I want to apply a function to list elements, two by two. I hoped that combn
would help me out, but I can't get it to work. A nested for-loop works, but
seems highly inefficient when you have large lists. Is there a more
efficient way of approaching this?
# Make some toy data
data(iris)
test<- vector("list",3)
for (i in 1:3){
x<- levels(iris$Species)[i]
tmp<- dist(iris[iris$Species==x,-5])
test[[i]]<- tmp
}
names(test)<- levels(iris$Species)
# Using 'lapply' and 'split' is a little bit more flexible:
test <- lapply(split(iris[, -5], iris$Species), function(x) dist(x))
# nested for loop works
for(i in 1:2){
for(j in (i+1):3){
print(all.equal(test[[i]],test[[j]]))
}
}
# combn doesn't work
combn(test,2,all.equal)
Sorry, no answer
HTH
Patrick
Cheers
Joris
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