search for: dimensions_003f

Hi, when I assign a one row matrix to another variable, then somehow R automatically convert that varaible into a list. For example: > a = matrix (12, 3, 4) > b = a[1,] > b [1] 12 12 12 12 Is there a way to enable R automatically make b as a one row matrix , rather than explicitly assign like matrix (b, ncol=1). I have come across a couple of time, that when I try to check how many

Hello Please see the example below > class(testX) [1] "matrix" > class(testX[1,]) [1] "numeric" Why not matrix? What am I missing here? Is there a way to keep the same class? The reason for the question is that I want to implement a k-step ahead prediction for my own routines and R wrecks does not seem to like [1,] as shown below. >

Hi All, I have vector containing 10 elements(odservations). I need to put this into a matrix, where the matrix should contain only one column. I need this to be done using the cbind command because in the final table I should have a column of attributes( from adifferent vector) and a column of vectors from the matrix above Please suggest me how this can be done Thanks and

There seems to be a result type difference when subscripting a 6 x 1 matrix as compared to a 3 x 2 matrix that is caused by the ncol = 1 compared to ncol > 1. > ThinMatrix <- matrix(1:6,ncol=1) > ThinMatrix [,1] [1,] 1 [2,] 2 [3,] 3 [4,] 4 [5,] 5 [6,] 6 > FatMatrix <- matrix(1:6,ncol=2) > FatMatrix [,1] [,2] [1,] 1 4 [2,] 2 5

Hi all, I've been wondering for a long time why R drops the dimensions of an array/matrix when you try to take a subset of one column. I mean this: dim(A) [1] 2 5 2 B=A[1,,] dim(B) 5 2 # so now dim(B)[3] doesn't work C=B[2,] dim(C) NULL # so now nrow(C) doesn't work Typically, you can get rid of this by writing as.matrix, as.array(...) but that generates extra lines of code.

Hi All, I'm hoping someone else can help me out with this. I am doing some matrix algebra using sub-parts of matrices, and sometimes I need only a single row/column of the original matrix. However, whenever I pull out only a single row/column, R returns a row vector, but often this will break my matrix algebra. Is there any *easy* way to get R to remember what the single row/column came out

Dear R users, Having searched the mail archive I think the conclusion was that it is not possible to have a column name when there is only one column in the matrix. But I thought I'd check with the more experienced users. What I tried to do was: in a loop I pick a column, record the column name and remove the column from the matrix. But when there were 2 columns left, after one column was

Hi all, Why subscripting a one column matrix drops one dimension? > x<- matrix(rnorm(100), ncol=1) > str(x) num [1:100, 1] -0.413 -0.845 -1.625 -1.393 0.507 ... > str(x[20:30,]) num [1:11] -0.315 -0.693 -0.771 0.448 0.204 ... > str(x[20:30]) num [1:11] -0.315 -0.693 -0.771 0.448 0.204 ... This breaks: > cov(x) [,1] [1,] 0.9600812 >

...t; > columns left, after one column was removed, the last column name > > disappeared by default. It means that I always miss out the last column. > > See R FAQ 7.5 Why do my matrices lose dimensions: > > > http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-do-my-matrices-lose-dimensions_003f > > which has some examples, along with ?Extract > > To wit: > > MAT <- matrix(1:12, ncol = 3) > > colnames(MAT) <- LETTERS[1:3] > > > MAT > A B C > [1,] 1 5 9 > [2,] 2 6 10 > [3,] 3 7 11 > [4,] 4 8 12 > > > > MAT[, 1] > [1]...