The R Book exemple Matrix and aggregate() -



The R Book exemple Matrix and aggregate() -

good evening,

i using "the r book" michael j. crawley. understand not best book learning r... have.

so in chapter 2 explain calculations on rows , columns. out of came question.

here series of command in r (r-studio) , have simple question ask.

x <- matrix(rpois(20, 1.5), nrow=4) x # [,1] [,2] [,3] [,4] [,5] #[1,] 2 2 0 0 2 #[2,] 2 1 0 0 2 #[3,] 1 0 1 2 0 #[4,] 2 1 2 0 2 grouping = c("a", "b", "b", "a") aggregate(x, list(group), sum) # ************** # group.1 v1 v2 v3 v4 v5 #1 4 3 2 0 4 #2 b 3 1 1 2 2

the question how did column titles (*) did appeared ...

v1 vector 1, v2 vector 2 ...

is intrinsic function aggregate()?

cheers

claude

from ?aggregate:

"the default method... coerces ‘x’ info frame , calls info frame method."

as.data.frame(x) gives vn column names:

as.data.frame(x) # v1 v2 v3 v4 v5 #1 0 1 1 0 2 #2 1 3 2 1 1 #3 1 3 2 0 0 #4 3 2 2 1 1

r

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