similar to: sampling without repetition

Displaying 20 results from an estimated 3000 matches similar to: "sampling without repetition"

2003 Nov 10
10
shuffling a vector
Hi, I'me trying to write a function that will shuffle a vector. At the moment I'm baically making a vector of randomized indices and then making a new vector from the original one using these random indices. However, is there an alternative (more elegant) method to do this? I tried help.search('shuffle') but it does'nt return anything relevant. Thanks,
2003 Nov 10
5
attaching data to any object
Hi, is the following possible - in a given session I make a lot of objects and save when exiting. Usually I note down seperately what each object is about. Is it possible to attach data to any object which would essentially be a short note explaining the meaning of it? Thanks, ------------------------------------------------------------------- Rajarshi Guha <rxg218 at psu.edu>
2005 May 26
5
a more elegant approach to getting the majority level
Hi, I have a factor and I would like to find the most frequent level. I think my current approach is a bit long winded and I was wondering if there was a more elegant way to do it: x <- factor(sample(1:0, 5,replace=TRUE)) levels(x)[ which( as.logical((table(x) == max(table(x)))) == TRUE ) ] (The length of x will always be an odd number, so I wont get a tie in max()) Thanks,
2004 Feb 06
3
a grep/regexpr problem
Hi, I'm trying to parse lines of the form: dan001.hin (0): fingerprint={256, 411, 426, 947, 973, 976} What I need is the sequence of number between {}. I'm using grep as match <- grep("{([0-9,\s]*)}",s,perl=T,value=T) where s is a character vector. But all I get is the whole string s. I tried using regexpr in an attempt to get just the sequence I wanted: match <-
2003 Oct 02
4
using a string as the formula in rlm
Hi, I am trying to build a series of rlm models. I have my data frame and the models will be built using various coulmns of the data frame. Thus a series of models would be m1 <- rlm(V1 ~ V2 + V3 + V4, data) m2 <- rlm(V1 ~ V2 + V5 + V7, data) m3 <- rlm(V1 ~ V2 + V8 + V9, data) I would like to automate this. Is it possible to use a string in place of the formula? I tried doing: fmla
2004 May 20
2
column sorting a matrix with indices returned
Hi, I'm trying to translate some Matlab code to R and I'm trying to implement the behavior of Matlab's sort() which when applied to a matrix will sort the columns returning the column sorted matrix as well as a matrix of permuted indices. Doing: > x <- matrix(c(3,4,2,6,3,4,8,7,5), nr=3) > x [,1] [,2] [,3] [1,] 3 6 8 [2,] 4 3 7 [3,] 2 4 5
2003 Dec 03
3
checking for identical columns in a mxn matrix
Hi, I have a rectangular matrix and I need to check whether any columns are identical or not. Currently I'm looping over the columns and checking each column with all the others with identical(). However, as experience has shown me, getting rid of loops is a good idea :) Would anybody have any suggestions as to how I could do this job more efficiently. (It would be nice to know which
2004 Mar 02
3
using object reference
Hi, I have read the previous thread on using references to objects in a function but the solution suggested does'nt seem to be working. basically I have an object x which has an attribute a containing some text. I would like to pass x to a function which will change the attribute a with some new text and have the change visible when the function exits. something like attr(x,'a')
2004 Mar 27
3
a question about scoping functions
Hi, I've written some helper functions which are used by another function (called func()). When func() is sourced I dont want the helper function to be seen in the global namespace (as shown by ls()). Currently what I have done is: func <- function() { helper1 <- function() { ... } helper2 <- function() { ... } # some code } Is there anyway to take the functions
2004 Sep 15
2
efficient submatrix extraction
Hi, I have a matrix of say 1024x1024 and I want to look at it in chunks. That is I'd like to divide into a series of submatrices of order 2x2. | 1 2 3 4 5 6 7 8 ... | | 1 2 3 4 5 6 7 8 ... | | 1 2 3 4 5 6 7 8 ... | | 1 2 3 4 5 6 7 8 ... | ... So the first submatrix would be | 1 2 | | 1 2 | the second one would be | 3 4 | | 3 4 | and so on. That is I want the matrix to be evenly divided
2003 Nov 21
3
speeding up a pairwise correlation calculation
Hi, I have a data.frame with 294 columns and 211 rows. I am calculating correlations between all pairs of columns (excluding column 1) and based on these correlation values I delete one column from any pair that shows a R^2 greater than a cuttoff value. (Rather than directly delete the column all I do is store the column number, and do the deletion later) The code I am using is: ndesc
2006 Jun 19
2
frechet distance
Hi, is there any package (or source code snippet) that will evaluate the Frechet distance for curves represented as sets of points? Searching around only threw up references to a Frechet distribution. Thanks, ------------------------------------------------------------------- Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net> GPG Fingerprint: 0CCA 8EE2 2EEB 25E2 AB04 06F7 1BB9
2005 Apr 04
5
a question about box counting
Hi, I have a set of x,y data points and each data point lies between (0,0) and (1,1). Of this set I have selected all those that lie in the lower triangle (of the plot of these points). What I would like to do is to divide the region (0,0) to (1,1) into cells of say, side = 0.01 and then count the number of cells that contain a point. My first approach is to generate the coordinates of these
2003 Oct 01
1
question about predictions with linear models
Hi, this question is probably very obvious but I just cant see where I might be going wrong. I'm using the lm() function to generate a linear model and then make predictions using a different set of data. To generate the model I do (tdata & pdata are matrices of observations and parameters, tdepv, pdepv are response vectors) x <- as.data.frame(tdata) x$tdepv <- tdepv
2003 Sep 30
2
subsetting a matrix
Hi, I'm trying to take a set of rows and columns out of a matrix. I hve been using the index aray approach. My overll matrix is X and is 179 x 65. I want to take out 4 columns and 161 rows. Thus I made a 161 x 2 array I and filled it up with the row,col indices. However doing, X[ I ] gives me a vector of the extracted elements. Is there anyway I can coerce this into a 161 x 4 matrix?
2004 Feb 12
2
variances of values predicted using a lm object
Hi, is there a function in R that will give me the variances of a predicted values obtained using predict.lm(). If no function is available I would need to calculate them myself - which involves taking the inverse of X'X (' indicating transpose) where X is my model matrix. I know that calculating an inverse directly is not a good idea in general - could anybody suggest a way around
2004 Jan 20
2
graph algorithms in R
Hi, I was wondering if there are any packages available that can represent mathematical graphs along with functions to manipulate them? Google did'nt turn up anything ( I may be asking too much of R :-/ ) Thanks, ------------------------------------------------------------------- Rajarshi Guha <rxg218 at psu.edu> <http://jijo.cjb.net> GPG Fingerprint: 0CCA 8EE2 2EEB 25E2 AB04
2004 Dec 05
1
matrix of 1,0's to a data.frame of factors
Hi, I have an integer matrix consisting of 1's and 0's and I would like to convert this to a data.frame where each column of the matrix becomes a factor variable. Now, some columns of the matrix have only 1's or only 0's as a result there is only 1 level for those columns in the data.frame. However it is required that each factor have 2 levels. So my solution is: m <-
2003 Sep 03
3
plotting a distribution curves
Hi, is there a way to plot distribution curves (say normal or chi sq etc) from within R? For example I looked up the *chisq family of functions but I'm not sure as to how I would use them to generate a plot of the chi sq distribution (for arbitrary d.o.f). Thanks, ------------------------------------------------------------------- Rajarshi Guha <rajarshi at presidency.com>
2004 Apr 19
1
using subscripts in a plot title with 2 lines
Hi, I'm making a plot in which the title takes up two lines. The title contains a subscript but when I look at the plot it does'nt seem tocome out properly. The code I'm using is: xtxt = expression(paste('Observed -log( ', IC[50], ' )')) ytxt = expression(paste('Predicted -log( ', IC[50], ' )')) mtxt = expression(paste('Plot of Observed