Stephen Berman
2022-Jun-13 21:47 UTC
[R] Why does qt() return Inf with certain negative ncp values?
Can anyone explain why Inf appears in the following results?> sapply(-1:-10, \(ncp) qt(1-1*(10^(-4+ncp)), 35, ncp))[1] 3.6527153 3.0627759 2.4158355 1.7380812 1.0506904 0.3700821 [7] Inf -0.9279783 -1.5341759 -2.1085213> sapply(seq(-6.9, -7.9, -0.1), \(ncp) qt(1-1*(10^(-4+ncp)), 35, ncp))[1] -0.2268386 Inf Inf Inf -0.4857400 -0.5497784 [7] -0.6135402 -0.6770143 -0.7401974 -0.8030853 -0.8656810 In case it matters:> sessionInfo()R Under development (unstable) (2022-06-05 r82452) Platform: x86_64-pc-linux-gnu (64-bit) Running under: Linux From Scratch r11.0-165 Matrix products: default BLAS: /usr/lib/R/lib/libRblas.so LAPACK: /usr/lib/R/lib/libRlapack.so locale: [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 [7] LC_PAPER=en_US.UTF-8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods base loaded via a namespace (and not attached): [1] compiler_4.3.0 tools_4.3.0 Thanks. Steve Berman
Bert Gunter
2022-Jun-14 02:28 UTC
[R] Why does qt() return Inf with certain negative ncp values?
Well, this will likely require close numerical analysis of the algorithm
used for the calculation, which I can't help with, but I do note for the
first case (I didn't bother checking the second) it may be useful to note
that besides returning Inf, I also got with -7 as ncp:
"There were 50 or more warnings"
all of which were:
"In qt(1 - 1 * (10^(-11)), 35, -7) :
full precision may not have been achieved in 'pnt{final}' "
I got this warning for all the other values of ncp also.
So it looks like: Congratulations, you seem to have defeated the algorithm.
Bert Gunter
"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Mon, Jun 13, 2022 at 6:14 PM Stephen Berman <stephen.berman at gmx.net>
wrote:
> Can anyone explain why Inf appears in the following results?
>
> > sapply(-1:-10, \(ncp) qt(1-1*(10^(-4+ncp)), 35, ncp))
> [1] 3.6527153 3.0627759 2.4158355 1.7380812 1.0506904 0.3700821
> [7] Inf -0.9279783 -1.5341759 -2.1085213
>
> > sapply(seq(-6.9, -7.9, -0.1), \(ncp) qt(1-1*(10^(-4+ncp)), 35, ncp))
> [1] -0.2268386 Inf Inf Inf -0.4857400 -0.5497784
> [7] -0.6135402 -0.6770143 -0.7401974 -0.8030853 -0.8656810
>
> In case it matters:
>
> > sessionInfo()
> R Under development (unstable) (2022-06-05 r82452)
> Platform: x86_64-pc-linux-gnu (64-bit)
> Running under: Linux From Scratch r11.0-165
>
> Matrix products: default
> BLAS: /usr/lib/R/lib/libRblas.so
> LAPACK: /usr/lib/R/lib/libRlapack.so
>
> locale:
> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
> [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
> [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
> [7] LC_PAPER=en_US.UTF-8 LC_NAME=C
> [9] LC_ADDRESS=C LC_TELEPHONE=C
> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
> loaded via a namespace (and not attached):
> [1] compiler_4.3.0 tools_4.3.0
>
> Thanks.
> Steve Berman
>
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