[R] Discovering methods

Gabor Grothendieck ggrothendieck at myway.com
Sat Nov 29 05:05:59 CET 2003

Sure, but why are some methods found using methods("POSIXct")
while other methods not found?

It would be nice to have some reliable documentation-independent 
way to discover all the methods for a class.

Date: Fri, 28 Nov 2003 23:17:45 -0400 
From: <kjetil at entelnet.bo>
To: <R-help at stat.math.ethz.ch>, <ggrothendieck at myway.com> 
Subject: Re: [R] Discovering methods 

On 28 Nov 2003 at 16:27, Gabor Grothendieck wrote:

How would I discover that + is a method for POSIXct? Applying
methods() to POSIXt and POSIXct does not reveal it.

will tell you.

Kjetil Halvorsen

> methods(class="POSIXt")
[1] as.character.POSIXt cut.POSIXt diff.POSIXt 
[4] hist.POSIXt julian.POSIXt months.POSIXt 
[7] quarters.POSIXt seq.POSIXt str.POSIXt 
[10] weekdays.POSIXt 

> methods(class="POSIXct")
[1] [.POSIXct [[.POSIXct [<-.POSIXct 
[4] all.equal.POSIXct as.data.frame.POSIXct c.POSIXct 
[7] format.POSIXct mean.POSIXct plot.POSIXct 

[10] print.POSIXct rep.POSIXct summary.POSIXct 

Applying methods() to "+" does give it but, in general, this 
would not be a feasible way to discover it since it would be
tantamount to trying everything possible:

> methods("+")
[1] +.POSIXt

Is there some other way?

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