similar to: apply() and dropped dimensions

Hi how do I extract those components of a list that satisfy a certain requirement? If jj <- list(list(a=1,b=4:7),list(a=5,b=3:6),list(a=10,b=4:5)) I want just the components of jj that have b[1] ==4 which in this case would be the first and third of jj, viz list (jj[[1]],jj[[3]]). How to do this efficiently? My only idea was to loop through jj, and set unwanted components to NULL,

Hi again everyone I have an arbitrarily dimensional array "a" and a list "jj" of length length(dim(a)). The elements of jj are vectors of indexes. How do I use do.call() to extract a[ jj[[1]], jj[[2]], jj[[3]], ...] ? Toy example follows: a <- matrix(1:30,5,6) jj <- list(5:1,6:1) I want the following a[ jj[[1]],jj[[2]] ] How do I do this? OBAttempts:

Hello everybody I'm using contour() to draw streamlines of potential flow, eg jj <- seq(from= -4, to=4,len=20) jj <- outer(jj,jj,function(x,y){x})+1i*outer(jj,jj,function(x,y){y}) f <- function(x){x^2} contour(Im(f(jj)), nlevels=44 , labels="") How best to put arrows on the contour lines to show the direction of flow? (ie I want contour lines looking like

Hi I have a two-column integer matrix like this: R> jj [,1] [,2] [1,] -1 1 [2,] -2 2 [3,] -7 6 [4,] -8 7 [5,] -6 5 [6,] -9 8 [7,] -5 4 [8,] 3 -3 [9,] -10 9 [10,] -4 3 I want a diagnostic that detects whether a row is a multiple of the first row or not. In this case, this would be rows 1,2, and 8. How to do this

Professor Ripley thanks for this. Very much appreciated. The original subject line reflected my late-night conviction that the answer might involve passing a strange list to do.call(). Anyway, package magic is broken (only in R-devel, I might add) because I have a function called "%eq%". R-2.0.0 CMD check is stopping (I think) because it interprets the "%" as a

Hello everyone I am trying to get one of my packages through R's QC. The package is clean for me under R-2.4.1, R-2.5.0, and R-devel, but Kurt gets > > * checking R code for possible problems ... WARNING > hypercube: no visible binding for global variable ?f? Function hypercube() [cut-&-pasted below] is intended to return an adjacency matrix for an n-dimensional

Hello List I have just written a little function that takes two matrices as arguments and returns a large matrix that is composed of the two input matrices in upper-left position and lower-right position with a padding value everywhere else. (function definition and toy example below). I need nonsquare matrices and rowname() and colname() inherited appropriately. Two questions: (1) Is there a

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" )

Hi If x <- 1:10 then x[5] <- 1i will promote x to be a complex vector. Suppose I have an S4 class "brob", and have functions is.brob(), as.brob(), as.numeric() and so forth (minimal self-contained code below). If x is numeric (1:10, say) and y is a brob, what is the best way to make x[5] <- y promote x to a brob in the same way as the complex example? Or is

Hello I am writing a replacement method for an S4 class and want to pass an additional argument to "[<-"() along the lines of "["()'s "drop" argument. Specifically, I have an S4 class, call it "foo", with a slot 'x' that is a vector and a slot 'NC' that is a scalar. I want to be able to pass a Boolean argument to the

Hi I have a square matrix Ainv of size N-by-N where N ~ 1000 I have a rectangular matrix H of size N by n where n ~ 4. I have a vector d of length N. I need X = solve(t(H) %*% Ainv %*% H) %*% t(H) %*% Ainv %*% d and H %*% X. It is possible to rewrite X in the recommended crossprod way: X <- solve(quad.form(Ainv, H), crossprod(crossprod(Ainv, H), d)) where quad.form() is a little

Hello list. I very often need 3d scatterplots, and use scatterplot3D quite a lot. I am trying to modify persp() to plot scatterplots, and make use of the theta and phi arguments that persp() offers. I am having some difficulty passing the correct arguments to persp(). Here is my function so far. Much of it is copied from the persp() manpage. points3d <- function(x,y,z,

Hello list. I very often need 3d scatterplots, and use scatterplot3D quite a lot. I am trying to modify persp() to plot scatterplots, and make use of the theta and phi arguments that persp() offers. I am having some difficulty passing the correct arguments to persp(). Here is my function so far. Much of it is copied from the persp() manpage. points3d <- function(x,y,z,

Hello, I am trying to vectorize the following loop but the vectorizer says: "Found a possible write-write reorder" and does not vectorize. Why? for (j=0; j < 8; j++) { jj = j << 3; m2[j][0] = diff[jj ] + diff[jj+4]; m2[j][1] = diff[jj+1] + diff[jj+5]; m2[j][2] = diff[jj+2] + diff[jj+6]; m2[j][3] = diff[jj+3] + diff[jj+7]; m2[j][4] = diff[jj ] -

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 I'm having difficulty with a multiple plot. What I want is 12 plots, all of which are the same size and shape, differing only in colour. Each one is a square, so there is an asp=1 in the plot call. I'm working in an Sweave environment so I am free to choose the height and width of the plot. I want the columns to be labelled at the head (here t=1,2,3) and the rows to be labelled at

I found out the other day that crossprod() will take a single matrix argument; crossprod(x) notionally returns crossprod(x,x). The two forms do not return identical matrices: x <- matrix(rnorm(3000000),ncol=3) M1 <- crossprod(x) M2 <- crossprod(x,x) R> max(abs(M1-M2)) [1] 1.932494e-08 But what really surprised me is that crossprod(x) is slower than crossprod(x,x): R>

Hi, I am sure this has come up before, but my searches of the archive didn't give any results (maybe I didn't use the right keywords, but if I use too many, the search times out). I have a vector of dimensions n, length is not fixed, eg n <- c(4,5,7) or n <- c(19,4,5,7) and a function f that takes a vector of indices, same length of n, and gives a scalar. I would like to fill

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 suppose I have two arrays x1,x2 of dimensions a1,b1,c1 and a2,b2,c2 respectively. I want x = x1 "+" x2 with dimensions c(max(a1,a2), max(b1,b2),max (c1,c2)) with x[a,b,c] = x1[a1,b1,c1] + x2[a2,b2,c2] if a <=min(a1,a2) , b<=min (b1,b2), c<=min(c1,c2) and the other bits either x1 or x2 or zero according to whether the coordinates are "in range" for