[Rd] R-1.9.0 Beta print.power.htest problem?
Marc Schwartz
MSchwartz at MedAnalytics.com
Wed Mar 31 20:44:25 CEST 2004
Hi all,
I just used power.t.test() in Version 1.9.0 beta (2004-03-31) today
under FC1.
The following is the output:
> power.t.test(delta = .5, power = .95, type = "paired")
$n
[1] 53.94062
$delta
[1] 0.5
$sd
[1] 1
$sig.level
[1] 0.05
$power
[1] 0.95
$alternative
[1] "two.sided"
$note
[1] "n is number of *pairs*, sd is std.dev. of *differences* within
pairs"
$method
[1] "Paired t test power calculation"
attr(,"class")
[1] "power.htest"
The following is the output from Version 1.8.1 Patched (2004-03-31):
> power.t.test(delta = .5, power = .95, type = "paired")
Paired t test power calculation
n = 53.94062
delta = 0.5
sd = 1
sig.level = 0.05
power = 0.95
alternative = two.sided
NOTE: n is number of *pairs*, sd is std.dev. of *differences* within
pairs
I have reviewed the following code for print.power.htest in power.R in
both 1.8.1 patched and the 1.9.0 Beta and do not see any differences, so
I am guessing that there is a methods issue here:
print.power.htest <-
function(x, ...)
{
cat("\n ", x$method, "\n\n")
note<-x$note
x[c("method","note")] <- NULL
cat(paste(format.char(names(x), width=15, flag="+"),
format(x), sep=" = "),sep="\n")
if(!is.null(note))
cat("\n", "NOTE:", note, "\n\n")
else
cat("\n")
}
Using 'methods(print)' in 1.8.1 patched, print.power.htest is listed,
while it is not listed in 1.9.0 beta, which would seem to reinforce a
methods problem.
The 1.8.1 patched NAMESPACE file for 'ctest' lists:
S3method(print, power.htest)
However, the NAMESPACE file for 'stats' in 1.9.0 Beta does not, so I am
guessing that this is the source of the problem?
Thanks,
Marc Schwartz
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