David,
I was not aware I could search through the list of available packages. Thanks
very much for the tip.
Regarding your guidance that my question may not have been appropriate for
R-help as it may not have been specifically an R question ... since it seemed
like an R question to me, are there any particular criteria that would help me
determine if my question is sufficiently specific to R to be appropriate for
R-help?
Thanks again,
Mauricio
On Monday, December 19, 2016 10:14 PM, David Winsemius
<[email protected]> wrote:
> On Dec 19, 2016, at 3:31 PM, David Winsemius <[email protected]> wrote:
>
>
>> On Dec 19, 2016, at 1:47 PM, Mauricio Cornejo via R-help
>> <[email protected]> wrote:
>>
>> Is there a function similar to stats::power.t.test that can handle unequal
>> variances from two samples?
>> I noticed that stats::t.test has an argument for indicating whether or not
>> to treat the two sample variances as equal. Wondering why
>> stats::power.t.test doesn’t have that option.
>> Thanks,Mauricio
>> [[alternative HTML version deleted]]
>
> Because R was developed by statisticians for statisticians and they assumed
> those other statisticians would know how to extend its functions when needed.
> But R-help is not advertised as the place to ask such questions when you
> don't have the statistical skills. (You might want to look at the code of
> `t.test` to see how you might construct appropriate arguments for
> `power.t.test` in the situation you imagine. Seems to me it should be fairly
> straightforward. `power.t.test` is built around the non-central
> t-distribution and solves a uniroot problem for the missing parameter among
> n, delta, power, sd, and sig.level, given the other 4 parameters.)
>
The other R-specific response might have been to teach you to use R's functions
to do a bit of searching:
?available.packages
old.opt <- options(available_packages_filters =
c("R_version", "CRAN", "duplicates"))
# saved options from prior state
avail <- available.packages()
names(avail)
NULL # oops, not a list.
> str( avail)
chr [1:9731, 1:17] "A3" "abbyyR" "abc" "ABCanalysis" ...
- attr(*, "dimnames")=List of 2
..$ : chr [1:9731] "A3" "abbyyR" "abc" "ABCanalysis" ...
..$ : chr [1:17] "Package" "Version" "Priority" "Depends" ...
colnames(avail)
#--- result---
[1] "Package" "Version"
[3] "Priority" "Depends"
[5] "Imports" "LinkingTo"
[7] "Suggests" "Enhances"
[9] "License" "License_is_FOSS"
[11] "License_restricts_use" "OS_type"
[13] "Archs" "MD5sum"
[15] "NeedsCompilation" "File"
[17] "Repository"
#---------
avail[ grepl("pow" ,avail[ ,"Package"] , ignore.case=TRUE), "Package"]
asypow bivarRIpower clusterPower
"asypow" "bivarRIpower" "clusterPower"
easypower fpow longpower
"easypower" "fpow" "longpower"
matpow mnormpow PharmPow
"matpow" "mnormpow" "PharmPow"
powell PoweR Power2Stage
"powell" "PoweR" "Power2Stage"
powerAnalysis powerbydesign powerGWASinteraction
"powerAnalysis" "powerbydesign" "powerGWASinteraction"
poweRlaw powerMediation powerpkg
"poweRlaw" "powerMediation" "powerpkg"
powerplus powerSurvEpi PowerTOST
"powerplus" "powerSurvEpi" "PowerTOST"
PowerUpR rPowerSampleSize twoStageGwasPower
"PowerUpR" "rPowerSampleSize" "twoStageGwasPower"
A more usable result:
names( avail[ grepl("pow" ,avail[ ,"Package"] , ignore.case=TRUE), "Package"] )
[1] "asypow" "bivarRIpower"
[3] "clusterPower" "easypower"
[5] "fpow" "longpower"
[7] "matpow" "mnormpow"
[9] "PharmPow" "powell"
[11] "PoweR" "Power2Stage"
[13] "powerAnalysis" "powerbydesign"
[15] "powerGWASinteraction" "poweRlaw"
[17] "powerMediation" "powerpkg"
[19] "powerplus" "powerSurvEpi"
[21] "PowerTOST" "PowerUpR"
[23] "rPowerSampleSize" "twoStageGwasPower"
options(old.opt) # reset options to default values
So you may find additional user-contributed power-oriented packages.
>
> --
>
> David Winsemius
> Alameda, CA, USA
>
> ______________________________________________
> [email protected] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius
Alameda, CA, USA
[[alternative HTML version deleted]]
______________________________________________
[email protected] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
