similar to: Friday question: negative zero

atan(1i) -> 0 + Inf i complex(1/5) -> 0.2 + 0i atan(1i) -> (0 + Inf i) * (0.2 + 0i) -> 0*0.2 + 0*0i + Inf i * 0.2 + Inf i * 0i infinity times zero is undefined -> 0 + 0i + Inf i + NaN * i^2 -> 0 + 0i + Inf i - NaN -> NaN + Inf i I am not sure how complex arithmetic could arrive at another answer. I advise against messing with infinities... use atan2() if you don't

>>>>> Richard O'Keefe >>>>> on Fri, 6 Sep 2024 17:24:07 +1200 writes: > The thing is that real*complex, complex*real, and complex/real are not > "complex arithmetic" in the requisite sense. > The complex numbers are a vector space over the reals, Yes, but they _also_ are field (and as others have argued mathematically only

> complex(real = 0, imaginary = Inf) [1] 0+Infi > Inf*1i [1] NaN+Infi >> complex(real = 0, imaginary = Inf)/5 [1] NaN+Infi See the Note in ?complex for the explanation, I think. Duncan can correct if I'm wrong. -- Bert On Thu, Sep 5, 2024 at 3:20?PM Leo Mada <leo.mada at syonic.eu> wrote: > Dear Bert, > > These behave like real divisions/multiplications: >

G.5.1 para 2 can be found in the C17 standard -- I actually have the final draft not the published standard. It's in earlier standards, I just didn't check earlier standards. Complex arithmetic was not in the first C standard (C89) but was in C99. The complex numbers do indeed form a field, and Z*W invokes an operation in that field when Z and W are both complex numbers. Z*R and R*Z,

The thing is that real*complex, complex*real, and complex/real are not "complex arithmetic" in the requisite sense. The complex numbers are a vector space over the reals, and complex*real and real*complex are vector*scalar and scalar*vector. For example, in the Ada programming language, we have function "*" (Left, Right : Complex) return Complex; function "*" (Left :

Hi all, What are current methods people use in R to identify mis-spelled column names when selecting columns from a data frame? Alice Johnson recently tackled this issue (see [BioC] posting below). Due to a mis-spelled column name ("FileName" instead of "Filename") which produced no warning, Alice spent a fair amount of time tracking down this bug. With my fumbling fingers

Hi, ?rawToChar 'rawToChar' converts raw bytes either to a single character string or a character vector of single bytes. (Note that a single character string could contain embedded nuls.) Allowing embedded nuls in a string might be an interesting experiment but it seems to cause some troubles to most of the string manipulation functions. A string with an embedded 0:

Dear list Maybe someone can help with the following problem: I have a source file containing the following code for plotting: pdf(file = 'data/mario/boxplot.pdf') bwplot(sig100 ~ target | group, data = fish, main = 'Boxplot der Signale in 100 Zellen nach Gruppe', xlab = '', ylab = 'Anzahl der Signale') dev.off() pdf(file = 'data/mario/xyplot.pdf')

I'm attempting to compile and install R version 1.7.1 for my statistical geneticists. It seems to compile correctly -- that is, it compiles without errors -- but the regression test is failing in the following manner: =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= > ## log > stopifnot(all.equal(log(1:10), log(1:10, exp(1)))) > stopifnot(all.equal(log10(30), log(30, 10))) >

On 'factor', I meant the case where 'levels' is not specified, where 'unique' is called. > factor(c(complex(real=NaN), complex(imaginary=NaN))) [1] NaN+0i <NA> Levels: NaN+0i Look at <NA> in the result above. Yes, it happens in earlier versions of R, too. On matching both NA and NaN, another consequence is that length(unique(.)) may depend on order.

Hi all, I believe this is a bug in the model.matrix function. I'd like a second opinion before filing a bug report. If I have a nested covariate B with multiple values for just one level of A, I can not get a non-singular design matrix out of model.matrix > df <- data.frame(A = factor(c("a", "a", "x", "x"), levels = c("x",

Dear all, We seem to have found a "strange" behaviour in the hyperbolic tangent function tanh on Windows. When running tanh(356 + 0i) the Windows result is NaN + 0.i while on Mac the result is 1 + 0i. It doesn't seem to be a floating point error because on Mac it is possible to run arbitrarily large numbers (say tanh(

On 2024-09-05 4:23 p.m., Leo Mada via R-help wrote: > Dear R Users, > > Is this desired behaviour? > I presume it's a bug. > > atan(1i) > # 0+Infi > > tan(atan(1i)) > # 0+1i > > atan(1i) / 5 > # NaN+Infi There's no need to involve atan() and tan() in this: > (0+Inf*1i)/5 [1] NaN+Infi Why do you think this is a bug? Duncan Murdoch

Dear Bert, These behave like real divisions/multiplications: complex(re=Inf, im = Inf) * 5 # Inf+Infi complex(re=-Inf, im = Inf) * 5 # -Inf+Infi The real division / multiplication should be faster and also is well behaved. I was expecting R to do the real division/multiplication on a complex number. Which R actually does for these very particular cases; but not when only Im(x) is Inf.

Should both parts of a complex number be printed to the same precision? The imaginary part of 0 looks a bit odd when log10(real/imag) >=~ getOption("digits"), but I'm not sure it is awful. Some people might expect the same number of significant digits in the two parts. > 1e7+4i [1] 10000000+0i > 1e7+5i [1] 10000000+0i > 1e10 + 1000i [1] 1e+10+0e+00i >

Hi: I am working with someone remotely to allow them access to our data. The follow command using "download.file" works perfectly on my Mac: > > download.file(url="http://oceanwatch.pfeg.noaa.gov:8081/thredds/ > wcs/satellite/AG/ssta/14day? > request=GetCoverage&version=1.0.0&service=WCS&format=NetCDF3&coverage= >

This is another follow-up to the thread from September "Recent changes to as.complex(NA_real_)". A test in data.table was broken by the changes for NA coercion to complex; the breakage essentially comes from c(NA, 0+1i) # vs c(as.complex(NA), 0+1i) The former is the output we tested against; the latter is essentially (via coerceVector() in C) what's generated by our

Full_Name: Pierre Legendre Version: 2.1.1 OS: Mac OSX 10.4.3 Submission from: (NULL) (132.204.120.81) I am reporting the mis-behaviour of the function 'eigen' in 'base', for the following input matrix: A <- matrix(c(2,3,4,-1,3,1,1,-2,0),3,3) eigen(A) I obtain the following results, which are incorrect for eigenvalues and eigenvectors 2 and 3 (incorrect imaginary portions):

That, for example, complex(real=NaN) and complex(imaginary=NaN) are regarded as equal makes it possible that length(unique(as.character(x))) > length(unique(x)) (current code of function 'factor' doesn't expect it). Yes, an argument for the behavior is that NA and NaN are of one kind. On my system, using 32-bit R for Windows from binary from CRAN, the result of sapply(z, match,

What am I missing? When I run the code below I get the error message "Error: ggplot2 doesn't know how to deal with data of class function" Googling suggests a message of "Error: ggplot2 doesn't know how to deal with data of class XXX" is not uncommon but I don't see why I am getting a "function" error unless I am using some reserved word?