On Oct 20, 2011, at 5:05 PM, Sarah Goslee wrote:
Hi,
Please send your information to the r-help list, not just to me, but
do
note that the list is plain-text only.
But surely all you are looking for is:
dt<-
c
(37,41,40,38,38,37,44,45,48,43,48,46,54,60,32,45,55,62,42,62,62,62,47,42,59,43,60,60,51,43,50,51,47,42,47,51
)
mean(dt)
[1] 48.16667
sd(dt)/sqrt(length(dt))
[1] 1.404923
I have no idea what bizarre formula SAS uses to calculate standard
error,
but the means match.
And you'll note that the lengthy R output you pasted in works just
fine,
and *does* include the standard errors and confidence limits *of the
groups you specified* in your formula. Maybe one of the excellent
introduction to R guides available online would be of use to you.
I suspect that Cem Girit is attempting to use survival::survfit and
survival::print.survfit, to get group means. (He also spelled his vT
variable differently in two places.) He seems confused about how to
offer arguments to the print.rmean and rmean paramters. He had been
advised by Therneau to read:
?print.survfit # where the details of the rmean calculation are
discussed
Both parameters are expecting a value of TRUE to be invoked, and he
was both misnaming them and mis-specifying them. Their default values
are:
> getOption('survfit.rmean')
NULL
> getOption("survfit.print.rmean")
NULL
After changing the name of "vt" to "vT":
> print(fit,print.rmean=TRUE)
Call: survfit.formula(formula = Surv(dT, vT) ~ gT)
records n.max n.start events *rmean *se(rmean) median
0.95LCL 0.95UCL
gT=DrugA 9 9 9 6 50.0 3.11 48
45 NA
gT=DrugB 9 9 9 3 54.8 2.93 NA
43 NA
gT=DrugC 9 9 9 4 53.8 2.74 NA
47 NA
gT=Vehicle 9 9 9 8 42.3 2.38 40
38 NA
* restricted mean with upper limit = 61
If an overall rmean were desired it would be obtained thusly:
> print(fit,print.rmean=TRUE)
Call: survfit.formula(formula = Surv(dT, vT) ~ 1)
records n.max n.start events *rmean *se(rmean)
median
36.0 36.0 36.0 21.0 50.5
1.7 47.0
0.95LCL 0.95UCL
43.0 NA
* restricted mean with upper limit = 62
--
David Winsemius, MD
West Hartford, CT
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