printing difftime summary

* David Winsemius <qjvafrzvhf at pbzpnfg.arg> [2012-11-25 00:50:51 -0800]:

On Nov 24, 2012, at 7:48 PM, Sam Steingold wrote:

* David Winsemius <qjvafrzvhf at pbzpnfg.arg> [2012-11-23 13:14:17
-0800]:

See http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-should-I-write-summary-methods_003f

--8<---------------cut here---------------start------------->8---
summary.difftime <- function (v) {
 s <- summary(as.numeric(v))
 r <- as.data.frame(sapply(s,difftime2string),stringsAsFactors=FALSE)
 names(r) <- c("string")
 r[[units(v)]] <- s
 class(r) <- c("data.frame","summary.difftime")
 r
}
print.summary.difftime <- function (sd) print.data.frame(sd)
--8<---------------cut here---------------end--------------->8---

it appears to work for a single vector:

--8<---------------cut here---------------start------------->8---

r1 <- summary(infl$delay)
r1

          string     secs
Min.    492.00 ms      0.5
1st Qu. 18.08 min   1085.0
Median   1.77 hrs   6370.0
Mean     8.20 hrs  29530.0
3rd Qu.  8.12 hrs  29250.0
Max.    6.98 days 602900.0

str(r1)

Classes 'summary.difftime' and 'data.frame':	6 obs. of  2 variables:
$ string: chr  "492.00 ms" "18.08 min" "1.77 hrs" "8.20 hrs" ...
$ secs  :Classes 'summaryDefault', 'table'  num [1:6] 4.92e-01
1.08e+03 6.37e+03 2.95e+04 2.92e+04 ...
--8<---------------cut here---------------end--------------->8---

but not as a part of data frame:

--8<---------------cut here---------------start------------->8---

a <- summary(infl)

Error in summary.difftime(X[[22L]], ...) :
 unused argument(s) (maxsum = 7, digits = 12)
--8<---------------cut here---------------end--------------->8---

I guess I should somehow accept a list of options in
summary.difftime()
and pass them on to the inner call to summary() (or should it be
explicitly summary.numeric()?)

In the usual way. If you know that the function will be called with
arguments from the summary.data.frame function then you should allow the
argument list to accept them. You can ignore them or provide provisions
for them. You just can't define your function to have only one argument
if you expect (as you should since you passes summary a dataframe
object) that it might be called within summary.data.frame.

This is the argument list for summary.data.frame:

  summary.data.frame

function (object, maxsum = 7, digits = max(3, getOption("digits") -
    3), ...)

how do I do that?

summary.difftime <- function (v, ... ) { ................

There are many asked and answered questions on rhelp about how to deal
with the "dots" arguments.