similar to: Change the index argument of a series

Why this kind of assignment does not work? n <- 1 f <- ifelse(n == 1, sin, cos) f(pi) this must be rewritten as: n <- 1 f <- cos if (n == 1) f <- sin f(pi) [oops. 1.224606e-16 instead of zero. Damn floating point errors :-/] Alberto Monteiro

Is there any way that I can do something like this: png("file.png", width=200, height=200) polygon(c(50, 50, 150, 150), c(50, 150, 150, 50)) dev.off() and then have a png file with a 100 x 100 pixels rectangle in the middle of it? It seems that when I call "plot", it redefines the image coordinates to some "optimized" value and then I lose any information to

How on Earth can I know what are the arguments of any of the functions of the tcl/tk package? I tried hard to find, using all search engines available, looking deep into keywords of R, python's tkinter and tcl/tk, but nowhere I found anything remotely similar to a help. For example, what are the possible arguments to tkgetOpenFile? I know that this works: library(tcltk) filename <-

Is there any function to write a XML structure, after it was read using xmlTreeParse? Ex: library(XML) x <- xmlTreeParse("Irpf2008/aplicacao/dados/12345678901/12345678901.xml") # write it... Alberto Monteiro PS: please, brazilians, don't be offended by my foul language!

Is there a simple way to plot a histogram with colors? For example, suppose I generate random points in the N(2,1) distribution: x <- rnorm(100000, mean = 2, sd = 1) Now I would like to plot the histogram: hist(x) but I would like to show the bars with x < 0 in red, and the bars with x >= 0 in lightgreen. Is there any simple way to do it? I think I can do it in two steps:

This is just my curiousity working. Suppose I write: f1 <- function(x) x + 1 f2 <- function(x) 2 * f1(x) f2(10) # 22 f1 <- function(x) x - 1 f2(10) # 18 This is quite obvious. But is there any way to define f2 in such a way that we "freeze" the definition of f1? f1 <- function(x) x + 1 f2 <- function(x) # put something here 2 * f1(x) # probably put something else here

I have a conceptual problem (sort of). Maybe there's a simple solution, maybe not. First, let me explain the test case that goes ok. Let x be a (fixed) n-dimensional vector. I simulate a lot of linear models, y = m x + c + error, then I do a lot of regressions. As expected, the estimated values of m (let's call them m.bar) are distributed according to a Student's t distribution.

Is there any generic function that gets the "home" directory? This should return /home/<user> in Linux and x:/Documents and Settings/<user> (or whatever) in Windows XP. Another (unrelated) question: what is the _simplest_ way to read and write R variables to/from files such that they are stored in a human-readable but R-like form? For example, if (say), x is a vector

Suppose that I have a matrix like: m <- rbind(c(1,2,3,4), c(2,3,2,1)) Is there any way to efficiently plot the _lines_ as if I was doing: plot(m[1,], type="l") points(m[2,], type="l", col="red") (of course, in the "real world" there much more than just 2 lines and 4 columns...) Alberto Monteiro

I mean, I can generate a expression, for example, with: z <- expression(x+y) But then how can I _use_ it? Is it possible to retrieve information from it, for example, that z is a sum, its first argument is x (or expression(x)) and its second argument is y? Alberto Monteiro

I want to make a plot, but instead of showing _numerical_ values, I would like to show _symbolic_ values. For example, I want to plot a function y = a x + b, where x varies between Xmin and Xmax. I would like the plot to show, in the x-axis, the strings Xmin and Xmax, instead of their numeric values. Is it possible? Alberto Monteiro

As a big fan of Wikipedia, it's frustrating to see how little there is about R in the correlated project, the Wikibooks: http://en.wikibooks.org/wiki/R_Programming Alberto Monteiro

Is there any way to write an imagematrix generated by the rimage package? Reproducible example: library(rimage) x <- read.jpeg(system.file("data", "cat.jpg", package="rimage")) png("newcat.png") plot(x) dev.off() The newcat.png image is different from the original file, because there are ugly white borders around it. Alberto Monteiro

Another pathological test. arima does not crash for that series that crashes arma: arima(c(2.01, 2.22, 2.09, 2.17, 2.42), order=c(1,0,0)) However, arima crashes for this: arima(c(1.71, 1.78, 1.95, 1.59, 2.13), order=c(1,0,0)) arima seems pretty consistent in its crashing behaviour, since crashing for one series means crashing for all affine series: lets.crash.arima <- c(71, 78, 95, 59,

Ooops! Sorry, I send it only to Uwe Ligges the first time. Best, Philippe Grosjean This is perhaps another solution, more elegant in the way the block comment is written... but it requires to redefine `!` and slows it a little bit because it tests first its arguments before calling .Primitive(!): It takes advantage of `!` being not defined for character arguments: > !2 [1] FALSE >

Is there any way to give a "decent" title after I plot something generated by decompose? For example: # generate something with period 12 x <- rnorm(600) + sin(2 * pi * (1:600) / 12) # transform to a monthy time series y <- ts(x, frequency=12, start=c(1950,1)) # decompose z <- decompose(y) # plot plot(z) Now, the title is the ugly "Decomposition of additive time

Dear R-experts, It is a quite stupid question but please help me. I am very confuced. I am able to import normal txt ant mat-files to R but unable to import .xls-file I do not understand the online help. Can please anyone send me the corresponding command lines? The .xls-file is attached. In my file we use commas for the decimal format (example: 0,712), changes might be needed. Thanks, Corinna

I need arguments pro-S-PLUS and against SAS for a meeting I will have next week. S-Plus is (90 - 99)% compatible with R, so using S-Plus will make things much easier for everyone. But I can't use this argument. What other arguments could I use? Alberto Monteiro

Hi everyone, I am interested in estimating this type of random effects panel: y_it = x'_it * beta + u_it + e_it u_it = rho * u_it-1 + d_it rho belongs to (-1, 1) where: u and e are independent and normally zero-mean distributed. d is also independently normally zero-mean distributed. So, I want random effects for group i to be correlated in t, following an AR(1) process. I am

I am writing a package which uses the Rgraphviz package which in turn uses the graph package, but my question does not (I believe) pertain specifically to the these packages so therefore I dare to post the question here: I my package I have a function "edges" which works on some graphs I have defined. However, there is also a function "edges" (or rather a generic method) in