similar to: Finding 'ncp' for t

Hi Folks, I note that, while the "chisq" functions dchisq(x, df, ncp=0, log = FALSE) pchisq(q, df, ncp=0, lower.tail = TRUE, log.p = FALSE) qchisq(p, df, ncp=0, lower.tail = TRUE, log.p = FALSE) rchisq(n, df, ncp=0) all have a slot for the non-centrality parameter "ncp", of the functions for the t and F distributions: dt(x, df, log = FALSE)

help(qt) states that: "ncp non-centrality parameter delta; currently except for rt(), only for abs(ncp) <= 37.62" so I would expect that calling qt with non-centrality parameter exceeding 37.62 should fail, instead e.g. calling > mapply(function(x) qt(p = 0.9, df = 55, ncp = x),35:45) gives: [1] 40.21448 41.35293 42.49164 43.68862 44.82945 45.97048 47.11170 48.25310 [9]

Hello all, Here's my query: Running R 1.6.2 on FreeBSD 5.0, and on WinXP, and I find that the following hangs the process: dchisq(alpha=0.01, df=1, ncp=295) but it does work for ncp < 294.92. Is this general? Best wishes to all, Andrew Andrew Robinson Ph: 208 885 7115 Department of Forest Resources Fa: 208 885 6226 University of Idaho E : andrewr at uidaho.edu PO

?pt states that ncp=0 is default, so this is correct > pt(3,3) [1] 0.9711656 > pt(3,3, ncp=0) [1] 0.9711656 but this is not > pt(-Inf,3) [1] 0 > pt(-Inf,3,ncp=0) [1] 0.5 is it? Torsten --please do not edit the information below-- Version: platform = i686-pc-linux-gnu arch = i686 os = linux-gnu system = i686, linux-gnu status = Under development (unstable) major = 1 minor

Dear R-users, I am wondering whether R implements a function returning the non central parameter of a t distribution (equivalent of the TnoncT function from SAS), given /x/ a value from a t distribution, /df /the degrees of freedom and /p/ the probability of x under this distribution. Thanks a lot, Matthieu -- Matthieu Dubois, /Ph.D/. /Student/ Cognitive Neuroscience Unit, UCL,

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 <<insert bug report here>> Reproduced on Debian and Windows ... On 2.4.x if you execute set.seed(12345) t.1 <- rt(n = 1000, df = 20) set.seed(12345) t.2 <- rt(n = 1000, df = 20, ncp = 0) all.equal(t.1, t.2) ## Not close to true This appears to be due to the fact that in 2.4.x rt is now rt function (n, df, ncp = 0) { if

The function 'pchisq' from the 'stats' library gives a wrong result if the argument equals exactly zero: # Upper tail of central 1-df chi^2 distribution > pchisq(1 , 1, ncp=0, lower.tail = F, log.p = FALSE) [1] 0.3173105 > pchisq(0.5 , 1, ncp=0, lower.tail = F, log.p = FALSE) [1] 0.4795001 > pchisq(0.01 , 1, ncp=0, lower.tail = F, log.p = FALSE) [1]

Dear List: The square of the noncentral t-statistic with noncentrality parameter \delta is a noncentral F with noncentrality parameter \lambda=\delta^2. So, t^2_{\nu,\delta} = F_{1,\nu,\lambda=\delta^2}. Consequently, it should follow that t^2_{1-\alpha/2,\nu,\delta} = f_{1-alpha,1,\vu,\lambda=\delta^2}. However, this is not what is happening with the following code. The central

Bug Description: Problem with the function pf() when the non-centrality parameter is large. Here is a sample command. You should see a smooth line from 0 to about 55, and then the values of pf() go crazy from 55 to 100. ############################ ncp <- seq(0,100,length=200) plot(ncp,pf(5,7,2,ncp=ncp)) ############################ Version: platform = i686-pc-linux-gnu arch = i686 os =

Hi, I've written some C code for density evaluation of the non-central t distribution. It works with the R-1.7.1 source code if placed in the src/nmath directory and after appropriate changes are made to Makefiles, to the dt function in src/library/base/R/distn.R etc. I haven't read a lot of R source code so it may need some R-ification, but I've tried to use the dt.c file as a

Full_Name: Jerry W. Lewis Version: 2.6.1 OS: Windows XP Professional Submission from: (NULL) (24.147.191.250) pchisq(0,0,ncp=lambda) returns 0 instead of exp(-lambda/2) pchisq(x,0,ncp=lambda) returns NaN instead of exp(-lambda/2)*(1 + SUM_{r=0}^infty ((lambda/2)^r / r!) pchisq(x, df + 2r)) qchisq(.7,0,ncp=1) returns 1.712252 instead of 0.701297103 qchisq(exp(-1/2),0,ncp=1) returns 1.238938

Full_Name: Long Qu Version: 2.3.1 OS: Windows XP Submission from: (NULL) (64.113.93.235) The QQ-plot of two versions of simulating noncentral F-distributed random numbers has quite different scales: > qqplot(rf(1000,2,15,3),qf(runif(1000),2,15,3)) The rf() function reads: > rf function (n, df1, df2, ncp = 0) { if (ncp == 0) .Internal(rf(n, df1, df2)) else rchisq(n, df1,

Full_Name: David Clayton Version: 1.8.1 OS: Linux Submission from: (NULL) (131.111.126.242) qchisq behaves very strangely when ncp is passed as zero (forcing internal qnchisq to be called) when first argument is small. Eg > qchisq(1-1e-6, 1, ncp=0, lower.tail=TRUE) qchisq(1-1e-6, 1, ncp=0, lower.tail=TRUE) [1] 1024 while, if ncp is unspecified, > qchisq(1-1e-6, 1) qchisq(1-1e-6, 1)

Hi all, I compiled 64-bit R on an Apple Mac G5 running OS X, but it failed make check. Simon Urbanek suggested I post results to R-devel. > On Nov 6, 2007, at 10:23 PM, Steven McKinney wrote: > > > Hi Simon, > > > > Would you be able to give more guidance on how to compile 64-bit > > libiconv for Tiger, > > You can get the sources from Apple and compile

Dear all, I want to see the source codes for "dchisq(x, df, ncp=0, log = FALSE)", but cannot find it. I input "dchisq" in the R interface, and then enter, the following message return: > dchisq /*****************************************************/ function (x, df, ncp = 0, log = FALSE) { if (missing(ncp)) .Internal(dchisq(x, df, log)) else

Does anybody has a function or idea how to calculate qt with a noncentrality parameter? I'm porting a SAS-macro for equivalence (Wellek, 1994 TT2ST) to R and it seems that I need this to calculate tinv (SAS-command, I hope that this is R's qt,...I get the SAS-macro manual next week). thanks Peter -- P.Malewski, Limmerstr.47, 30451 Hannover, 0511-2135008 At work:

Full_Name: Drouilhet R?my Version: 1.8.1 OS: Linux Submission from: (NULL) (195.221.43.136) qchisq(1,10) works well but qchisq(1,10,ncp=0) does not work whereas ncp=0 is the default value of the function qchisq(1,10). (of course, 10 will be replaced by any integer value). Let us notice that this bug occurs only when applying probability one. (qchisq(seq(0,.9,.1),10,ncp=0) works very well).

Dear all, The help page on the t distribution says: The most used applications are power calculations for t-tests: Let T= (mX - m0) / (S/sqrt(n)) where mX is the `mean' and S the sample standard deviation (`sd') of X_1,X_2,...,X_n which are i.i.d. N(mu,sigma^2). Then T is distributed as non-centrally t with `df'= n-1 degrees of freedom and non-centrality

Hi everyone, I tried to use yum to search for ncpfs-2.2.1-1.i386.rpm, but it couldn't find it. I googled and found this package is included with redhat,but i'm not sure if it's included with CentOS 4.2. Any idea where I can find and install it using yum? Thanks JC

I was wondering how do I actually see what's inside a function, say, density of t distribution, dt()? I know for some, I can type the function name inside R and the code will be displayed. But for dt(), I get > dt function (x, df, ncp, log = FALSE) { if (missing(ncp)) .Internal(dt(x, df, log)) else .Internal(dnt(x, df, ncp, log)) } <environment: namespace:stats> I