Thanks to all for the help. I have learned much about "inherit" and
"class". I like to know about one additional option, and that is to use
a calling parameter without the quotation marks, similar to the linear
regression syntax:
lm(data=mydata,weights=wt)
Below is a simple set of codes to calculate weighted means with
generated data in data frame "mydata". As annotated below, I like the
following call to work (without the quotations):
wmean(mydata,wt=weight)
Thank you!
----
mydata<-matrix(1:20,ncol=2)
mydata<-cbind(mydata,runif(10,0,1))
colnames(mydata)<-c("y","x","weight")
mydata<-as.data.frame(mydata)
wmean <- function(data,wt){
if (inherits(wt,what="character")) wt<-data[,wt]
wt<-wt/mean(wt)
Mean<-NULL
for (i in 1:ncol(data)){
Mean[i] <- sum(data[,i]*wt)/sum(wt)
}
list("Mean: ",Mean)
}
wmean(mydata,wt="weight") # This works
wmean(mydata,wt=weight) # <= Like this to work
reg<-lm(data=mydata,weights=weight) # ? lm
On 6/24/2015 3:20 AM, Martin Maechler wrote:
Steve Taylor <steve.tay...@aut.ac.nz>
on Wed, 24 Jun 2015 00:56:26 +0000 writes:
> Note that objects can have more than one class, in which case your ==
and %in% might not work as expected.
> Better to use inherits().
> cheers,
> Steve
Yes indeed, as Steve said, really do!
The use of (class(.) == "....") it is error prone and
against the philosophy of classes (S3 or S4 or ..) in R :
Classes can "extend" other classes or "inherit" from them;
S3 examples in "base R" are
- glm() objects which are "glm"
but also inherit from "lm"
- multivariate time-series are "mts" and "ts"
- The time-date objects POSIXt , POSIXct, POSIXlt
==> do work with inherits(<obj>, <class))
or possibly is( <obj>, <class>)
We've seen this use of
class(.) == ".." (or '!=" or %in% ...)
in too many places; though it may work fine in your test cases,
it is wrong to be used in generality e.g. inside a function you
provide for more general use,
and is best replaced with the use of inherits() / is()
everywhere "out of principle".
Martin Maechler
ETH Zurich
--
Steven Yen
My e-mail alert:
https://youtu.be/9UwEAruhyhY?list=PLpwR3gb9OGHP1BzgVuO9iIDdogVOijCtO
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