> On Dec 19, 2016, at 3:31 PM, David Winsemius <dwinsem...@comcast.net> wrote: > > >> On Dec 19, 2016, at 1:47 PM, Mauricio Cornejo via R-help >> <r-help@r-project.org> 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 > > ______________________________________________ > R-help@r-project.org 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 ______________________________________________ R-help@r-project.org 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.