Displaying 20 results from an estimated 10000 matches similar to: "Spare matrix multiplication"
2013 Jan 14
2
The three-dot question
Dear all,
Why does not the three-dot accept arguments from the parent environment?
I am just confused with this error, can someone give me a hint?
> rm(list=ls())
> testFun <- function(a, ...)
+ {
+ if(a){
+ print(a)
+ }else
+ {
+ print(b)
+ }
+ }
>
> myTask <- function(a)
+ {
+ b <- 3
+ testFun(a, b = b)
+ }
>
2011 Jan 12
2
How to disable using "enter" key to exit the browser in debugging mode
Dear R,
How can I disable using "enter" key to exit the browser() in debug mode? I
would love to have this option because it is so annoying to jump out of the
debugging mode unexpectedly when I don't want to. I guess some of us have
encouraged at least one of these situations,
1, Accidentally pressed the enter key within the browser.
2, Copy and paste a piece of debugging code
2011 Jan 18
2
Convert a matrix's columns to list
Dear R,
Is there an efficient way to make a list that each element is from the
corresponding column of a matrix. For example, if I have a matrix "a"
> a <- matrix(1:10, 5, 2)
> a
[,1] [,2]
[1,] 1 6
[2,] 2 7
[3,] 3 8
[4,] 4 9
[5,] 5 10
I would like to have a list "b" like this
> b <- list(a[, 1], a[, 2])
> b
[[1]]
[1] 1 2 3
2010 Oct 12
1
lapply to subsets
Dear R,
I have a silly question concerns with *apply. Say I have a list called A,
A <- list(a = array(1:20, c(2, 2, 5)), b = array(1:30, c(2, 3, 5)))
I wish to calculate the mean of A$a, and A$b w.r.t. their third dimension so
I did
lapply(A,apply,c(1,2),mean)
Now if I still wish to do the above task but take away some burn-in, e.g. do
not take A$a[,,1:2],and A$b[,,1:2] into account.
2010 Sep 24
3
boundary check
Dear R,
I have a covariates matrix with 10 observations, e.g.
> X <- matrix(rnorm(50), 10, 5)
> X
[,1] [,2] [,3] [,4] [,5]
[1,] 0.24857135 0.30880745 -1.44118657 1.10229027 1.0526010
[2,] 1.24316806 0.36275370 -0.40096866 -0.24387888 -1.5324384
[3,] -0.33504014 0.42996246 0.03902479 -0.84778875 -2.4754644
[4,] 0.06710229 1.01950917
2009 Nov 05
2
rm(list<-ls()) error
Dear R,
Why rm(list<-ls()) gives an error but rm(list=ls()) not?. I remember the
operator ‘<-’ can be used anywhere...
Thanks!
Feng
--
Feng Li
Department of Statistics
Stockholm University
106 91 Stockholm, Sweden
http://feng.li/
[[alternative HTML version deleted]]
2010 Jan 05
1
R-package related to the topic of INARMA models
Dear R,
I am looking for R-package related to INARMA (Integer-valued ARMA). Can
anyone give me some information? I did not get information from task view.
Many thanks.
Feng
--
Feng Li
Department of Statistics
Stockholm University
106 91 Stockholm, Sweden
http://feng.li/
[[alternative HTML version deleted]]
2011 Mar 23
1
R gui problem for windows
Dear R,
I rare use the standard R-gui on Windows. Yesterday I tried the latest
stable release on Windows 7 and XP and found one thing interesting. Assume
currently I am running R code, say
> example(plot)
Then I click the "close window" button on the R main window. R asks me to
save workspace image or not. Then I click "cancel". I suspect that my
program
2011 Feb 01
1
kmeans: number of cluster centres must lie between 1 and nrow(x)
Dear R,
Can't I cluster a dataset into k clusters where k is exactly the number of
observations? I have version 12.2 installed. See this example
> a <- matrix(1:100, 20)
> kmeans(a, 20)
Error: number of cluster centres must lie between 1 and nrow(x)
This is a bit ad-hoc but I known R from version 2.12 allows number of
clusters to be one. So I guess allowing number of clusters to be
2009 Feb 11
5
How to handle large numbers?
Dear R,
I have two questions:
1, Why both R and Matlab give 0*Inf==NaN? To my knowledge, it should be zero
mathematically. Am I right?
2, I need to calculate e.g. exp(a)/(exp(b)+c), where both a and b are very
large numbers (>>1000, e.g a=1000, b=1007, and c=5). R gives me NaN when I
use the following command:
> exp(1000)/(exp(1007)+5)
[1] NaN
I am pretty sure this should be close to
2009 Mar 11
1
matrix multiplication, tensor product, block-diagonal and fast computation
Dear R-users,
I am searching to the "best" way to compute a series of n matrix
multiplications between each matrix (mXm) in an array (mXmXn), and each
column of a matrix (mXn).
Please find below an example with four possible solutions.
The first is a simple for-loop which one might avoid; the second
solution employs the tensor product but then manually selects the right
outcomes. The
2011 Mar 16
2
Singularity problem
Dear R,
If I have remembered correctly, a square matrix is singular if and only if
its determinant is zero. I am a bit confused by the following code error.
Can someone give me a hint?
> a <- matrix(c(1e20,1e2,1e3,1e3),2)
> det(a)
[1] 1e+23
> solve(a)
Error in solve.default(a) :
system is computationally singular: reciprocal condition number = 1e-17
Thanks in advance!
Feng
--
2010 Sep 13
2
How to generate a particular sequence ?
Dear R,
I have a vector, say a = c(1,2,4,5,6,8). Can I generate a vector or array
(2-by-3-by-3) of this form c(1,2,1,2,1,2,4,5,4,5,4,5,6,8,6,8,6,8), in which
every two elements in "a" have been repeated twice?
I am to stupid today and could not figure this simple question out... Many
many thanks!
Feng
--
Feng Li
Department of Statistics
Stockholm University
106 91 Stockholm,
2010 Sep 07
4
a^c(1:3)
Dear R,
I have two small questions confused me recently. Now assume I have a matrix
"a", like this,
> a <- matrix(1:6, 2, 3)
> a
[,1] [,2] [,3]
[1,] 1 3 5
[2,] 2 4 6
I sometimes need each row of "a" raised to a different exponent. So I do a
trick like this,
> a^c(2, 3)
[,1] [,2] [,3]
[1,] 1 9 25
[2,] 8 64 216
My first
2011 Feb 26
1
Wired behavior of a 2-by-2 matrix indicies
Dear R,
I found a very wired behavior for a 2-by-2 matrix, see this example
> A <- matrix(1:4, 2)
> idx4A <- matrix(1:4, 2)
> A[idx4A]
Error in A[idx4A] : subscript out of bounds
But other matrices are fine,
> B <- matrix(1:9, 3)
> idx4B <- matrix(1:9, 3)
> B[idx4B]
[1] 1 2 3 4 5 6 7 8 9
I can reproduce this for both 32bit windows and 64bit linux with R 2.12.1
2009 Feb 04
3
Passing data among multiple instances
Dear R,
I have two R instances running at the same time, say instance A and instance
B. Is there a simpler way to pass the data in A to B?
More precise, I have a stupid example:
In instance A, I am running a function "test1"
test1 <- function (x1)
{
x2 <- sin(x1)
return(x2)
}
In instance B, another function "test2"
test2 <- function (x2)
{
x3 <-
2007 Oct 10
3
as.dist with diagonal unequal zero
Hello and sorry that I still haven?t found a solution for my problem.
I need to extract the lower and upper triangle from a square matrix
including the diagonal. This diagonal is not zero in that special case.
I tried with as.dist
w<-as.dist(w, diag = TRUE)
> w
1 2 3 4 5
1 0
2 2 0
3 3 8 0
4 4 9 14 0
5 5 10 15 20 0
but found no way to keep the diagonal that is in the
2012 Apr 13
4
#!/usr/bin/env Rscript --vanilla ??
I think that's my first true question (rather than answer)
to R-help.
As R has, for a long time, become my primary scripting and
programming language, I'm prefering at times to write Rscript
files instead of shell scripts, notably when R has nice ways to
do some of the things.
On a standard standalone platform with standard R,
I would start such a script with
2010 Oct 05
2
Intel i7 utilization
Hello,
Is there a way to force through R the amount of the cpu's cores (or the
cpu's utilization level) used under Windows 7 or Linux?
Thanks,
Costas
2009 Aug 06
1
solving system of equations involving non-linearities
Hi,
I would appreciate if someone could help me on track with this problem.
I want to compute some parameters from a system of equations given a number of sample observations. The system looks like this:
sum_i( A+b_i>0 & A+b_i>C+d_i) = x
sum_i( C+d_i>0 & C+d_i>A+b_i) = y
sum_i( exp(E+f_i) * ( A+b_i>0 & A+b_i>C+d_i) = z
A, C, E are free variables while the other