On Jul 7, 2011, at 8:52 PM, David Winsemius wrote:
On Jul 7, 2011, at 8:47 PM, Gang Chen wrote:
I define the following function to convert a t-value with degrees
of freedom
DF to another t-value with different degrees of freedom fullDF:
tConvert <- function(tval, DF, fullDF) ifelse(DF>=1, qt(pt(tval, DF),
fullDF), 0)
It works as expected with the following case:
tConvert(c(2,3), c(10,12), 12)
[1] 1.961905 3.000000
However, it gives me warning for the example below although the
output is
still as intended:
tConvert(c(2,3), c(0,12), 12)
[1] 0 3
Warning message:
In pt(q, df, lower.tail, log.p) : NaNs produced
I'm confused about the warning especially considering the fact that
the
following works correctly without such warning:
tConvert(2, 0, 12)
[1] 0
What am I missing?
The fact that ifelse evaluates both sides of the consequent and
alternative.
I also think you should update yur R to the most recent version since
a current version does not issue that warning.
--
David Winsemius, MD
West Hartford, CT
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