similar to: partial match gotcha

Hi I used write() the other day to save some results. It seems that write() does not record the full precision of the objects being written: > write(pi,file="~/f",ncolumns=1) > pi.saved <- scan("~/f") Read 1 item > dput(pi) 3.14159265358979 > dput(pi.saved) 3.141593 > pi-pi.saved [1] -3.464102e-07 > This difficulty was particularly difficult to

The following gotcha caught me off-guard just now. I have two matrices, a and b: a <- matrix(1,3,3) b <- matrix(1,1,1) (note that both "a" and "b" are matrices). I want them in a list: > B <- NULL > B[[1]] <- a > B[[2]] <- b > B [[1]] [,1] [,2] [,3] [1,] 1 1 1 [2,] 1 1 1 [3,] 1 1 1 [[2]] [,1] [1,] 1

Hi I have two arbitrarily dimensioned arrays, "a" and "b", with length(dim(a))==length(dim(b)). I want to form a sort of "corner-to-corner" version of abind(), or a multidimensional version of blockdiag(). In the case of matrices, the function is easy to write and if a=matrix(1,3,4) and b=matrix(2,2,2), then adiag(a,b) would return: [,1] [,2] [,3] [,4] [,5]

Hi the following gave me a shock: > atan(2) [1] 1.107149 > atan(2+0i) [1] -0.4636476+0i > or, perhaps more of a gotcha: > atan(1.0001+0i) [1] -0.7853482+0i > atan(0.9999+0i) [1] 0.7853482+0i > evidently atan()'s branch cuts aren't where I thought they were. Where do I look for documentation on this? -- Robin Hankin Uncertainty Analyst National

Hi try this: p3dpairs <- function(x,x1, xlim=NULL,ylim=NULL,zlim=NULL,col=par("col"), pch=par("pch"), cex=par("cex"), ...){ if(is.matrix(x)){ z <- x[,3] y <- x[,2] x <- x[,1] } if(is.matrix(x1)){ z1 <- x1[,3] y1 <- x1[,2] x1 <- x1[,1] } if(missing(zlim)) { z.grid <-

Hi has anyone coded up domain colouring for visualizing complex analytic functions (such as elliptic functions)? [ the idea is to depict a complex function f(z) using a filled.contour() variant in which the hue is given by Arg(f(z)), and the saturation by Mod(f(z)). ] -- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre European Way, Southampton SO14 3ZH, UK tel

Hi One of my packages needs a look-up table of pre-calculated numbers in the data directory. I would like to have the matrix as large as possible. What is the largest size matrix that would be an acceptable datafile in an R package? [ The table is a square, upper triangular matrix consisting of logs of Stirling numbers calculated by Maple. As discussed on the List a few days ago (thanks

Hi If I have a <- Inf + 1i then Re(a) is Inf, and Im(a) is 1, as expected. But if b <- 1 + Inf * 1i, then Im(b) = Inf , as expected, but Re(b) = NaN, which I didn't expect. Why this asymmetry? How to define an object with Re(b)=1, Im(b)=Inf? -- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre European Way, Southampton SO14 3ZH, UK tel 023-8059-7743

Hi If I do this: par(mfrow=c(2,2)) persp(matrix(1:4,6,6),box=F,phi=33,theta=33) persp(matrix(1:4,6,6),box=F,phi=33,theta=33) persp(matrix(1:4,6,6),box=F,phi=33,theta=33) persp(matrix(1:4,6,6),box=F,phi=33,theta=33) ( or indeed layout(matrix(1:4,2,2)) persp . . . . ) then the mesh plots look too small to me. How do I make them larger? -- Robin Hankin Uncertainty Analyst National

Hi ?atan2 says that atan2(y,x)=atan(y/x) for x and y numeric or complex vectors. Well, I would expect atan2(1,1i) to be equal to atan(-1i), but > atan2(1,1i) Error in atan2(y, x) : Non-numeric argument to mathematical function > R.version _ platform powerpc-apple-darwin8.5.0 arch powerpc os darwin8.5.0 system powerpc, darwin8.5.0

Hi ?atan2 says that atan2(y,x)=atan(y/x) for x and y numeric or complex vectors. Well, I would expect atan2(1,1i) to be equal to atan(-1i), but > atan2(1,1i) Error in atan2(y, x) : Non-numeric argument to mathematical function > R.version _ platform powerpc-apple-darwin8.5.0 arch powerpc os darwin8.5.0 system powerpc, darwin8.5.0

Hi ?lines says For 'type = "h"', 'col' can be a vector and will be recycled as needed. Why doesn't lines() recycle colours for other types? If I type > plot(0:1,0:1,type="n") > lines(runif(11),runif(11),col=c("red","green")) > then all ten lines are red, with no warning given. Is there a reason why

How do I draw non-square matrices with image() and get the axes right? Try 1: a <- matrix(rnorm(100),20,5) image(1:20,1:5,a,asp=1,xlab="label here") # No good because the axes don't touch the image Try 2: image(1:20,1:5,a,asp=1,axes=F,xlab="label here") axis(side=1,pos=0) # No good because the x axis label is floating far from the x axis. Try 3:

Hi I have several methods for evaluating a function. The methods are algebraically identical but use different numerical techniques. The different methods work better (converge faster, etc) in different parts of the function's domain. I am compiling a test suite for a package, and would like to verify that the different methods return approximately identical results. Toy example

Hi I have been looking at complex.c and want to access z_cos() and z_sin () from C in one of my packages. There doesn't seem to be a corresponding header file: there is no complex.h file. Where are the prototypes of z_sin() and z_cos() for these functions? grepping didn't help me: find ~/downloads/R-2.1.1/ -name "*.h " | xargs egrep "z_cos"

Hi section 6.1 of R-exts suggests that a package can take over a function in the base package and make it generic. I want to do this with Re() and have the following lines in my R code: "Re" <- function(x){UseMethod("Re" )} "Re.default" <- get("Re" ,pos=NULL,mode="function") "Re.octonion" <- function(x){give.comp(x,1)}

Hi In V&R the "polynomial" class is explicitly specified to have no logical operators: setMethod("Logic", signature(e1="polynomial"), function(e1,e2){stop ("...")}) I too have a class of objects for which I want to specify that Logic operators do not work, but executing setClass("brob", representation = representation

Hi How do I test for an object having a particular virtual class? In the following, "onion" is a virtual class, and "octonion" is a non-virtual class contained in onion. The last call to inherits() gives FALSE [R-2.5.0], when inherits.Rd led me to expect TRUE. setClass("onion", representation = "VIRTUAL" )

In complex analysis, Cauchy's integral theorem states (loosely speaking) that the path integral of any entire differentiable function, around any closed curve, is zero. I would like to see this numerically, using R (and indeed I would like to use the residue theorem as well). Has anyone coded up path integration? -- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre

Hi just now I had an apparently insurmountable problem that's been bugging me for days, but phrasing my question in a form suitable for the R-help list enabled me to solve my own problem in two minutes flat. thanks everyone. -- Robin Hankin Uncertainty Analyst Southampton Oceanography Centre European Way, Southampton SO14 3ZH, UK tel 023-8059-7743