[R] Question on the idiom: start <- coef; start[fit$pivot] <- coef
Barnet Wagman
wagman at enteract.com
Fri Apr 30 09:36:59 CEST 1999
I wonder if someone could explain how the following R idiom works (it's
used in
glm.fit).
start <- coef
start[fit$pivot] <- coef
coef is a vector of coefficients, set by .Fortran("dqrls", ...).
fit$pivot is a vector of integer indexes (indicating how dqrls permuted
the columns
of x). If coef has n elements, fit$pivot is a permutation of seq(1,5).
start[fit$pivot] is simple enough, but the assignment performs a futher
permuation
that I don't understand. For example
> pivot <- c(1,3,4,2,5)
> a <- c(100,200,300,400,500)
> b <- a
> b[pivot] <- a
> b
[1] 100 400 200 300 500
I guess there must be a replacement function for [], but I haven't
been able to dig up any documentation on it (and I'm not quite sure
where
to look in the source code). I'd like to understand what R does when a
vector
is assigned to another vector in this way.
Thanks,
(and thanks for all the other help I've gotten from member of the list
lately)
-------------------
Barnet Wagman
wagman at enteract.com
773-645-8369
1361 N. Hoyne
Chicago, IL 60622
--------------------
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
More information about the R-help
mailing list