dear Duncan,
Thank you very much for your quick reply. Very useful and also very
elegant, I would add.
Thanks again,
kind regards,
Vito
Il 08/05/2024 14:06, Duncan Murdoch ha scritto:
I would guess that subsetting uses [] indexing on each column, with a
logical argument. If that is true, then one solution (which is less
direct, but maybe someone would call it elegant) is to put a class on
the result of `f()`, and define a `[` method for that class that
preserves the attributes you want to preserve.
In your example:
f <- function(x) {
attr(x, "vi") <- length(x)
class(x) <- c("withAttributes", class(x))
x
}
`[.withAttributes` <- function(x, i) {
subset <- NextMethod()
attr(subset, "vi") <- attr(x, "vi")
subset
}
x<- 1:5
z<-runif(5)
y<-rnorm(5)
mf <- model.frame(y~f(z), subset=x>=3)
attr(mf[,2],"vi") #it works
#> [1] 5
--
=================================================
Vito M.R. Muggeo, PhD
Professor of Statistics
Dip.to Sc Econom, Az e Statistiche
Università di Palermo
viale delle Scienze, edificio 13
90128 Palermo - ITALY
tel: 091 23895240; fax: 091 485726
http://www.unipa.it/persone/docenti/m/vito.muggeo
Assoc Editor: Statist Modelling, Statist Meth Appl
past chair, Statistical Modelling Society
coordinator, PhD Program in Econ, Businss, Statist
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