# search for: solve

Displaying 20 results from an estimated 28432 matches for "solve".

2000 Apr 28
3
Matrix inverse
I haven't found a function that directly calculates the matrix inverse, does it exist? Otherwise what would be the fastest way to do it? Patrik Waldmann -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or
2016 Apr 20
6
Solving sparse, singular systems of equations
I have a situation in R where I would like to find any x (if one exists) that solves the linear system of equations Ax = b, where A is square, sparse, and singular, and b is a vector. Here is some code that mimics my issue with a relatively simple A and b, along with three other methods of solving this system that I found online, two of which give me an error and one of which succ...
2009 May 15
1
...u/uploads/20090522/7a0d0313f21fd6a8/Bonacich%20Power.RData > Graph size *Vertices: 20924 Edges: 146938 Directed: FALSE No graph attributes. Vertex attributes: name. No edge attributes. * computer Configuration *WIndows XP service Pack 3 .0 GB RAM* I am using SPARSE matrix to solve the problem This is the code I use to obtain bonpower using Sparse Matrix & alternatively the code is in the following website http://igraph.wikidot.com/r-recipes#toc6 *bonpow.sparse <- function(graph, nodes=V(graph), loops=FALSE, exponent=1, rescale=T...
2003 Aug 07
3
ginv vs. solve
Why do x<-b%*%ginv(A) and x<-solve(A,b) give different results?. It seems that I am missing some basic feature of matrix indexing. e.g.: A<-matrix(c(0,-4,4,0),nrow=2,ncol=2) b<-c(-16,0) x<-b%*%ginv(A);x x<-solve(A,b);x Thanks in advance, Angel
2016 Apr 20
0
Solving sparse, singular systems of equations
...u really want to proceed. See also ?svd and package irlba. -- Sent from my phone. Please excuse my brevity. On April 20, 2016 4:22:34 AM PDT, A A via R-help <r-help at r-project.org> wrote: > > > >I have a situation in R where I would like to find any x (if one >exists) that solves the linear system of equations Ax = b, where A is >square, sparse, and singular, and b is a vector. Here is some code that >mimics my issue with a relatively simple A and b, along with three >other methods of solving this system that I found online, two of which >give me an error and o...
2003 Jun 02
1
Help with factorized argument in solve.QP
Hi I'm having problems getting the "factorized" argument in solve.QP (part of the quadprog library) to work as expected. The helpfile states that when the factorized argument is set to TRUE, then the function requires the inverse of a square-root factor of the Hessian instead of the Hessian itself. That is, when factorized=TRUE, the Dmat argument should be a matr...
2016 Apr 20
0
Solving sparse, singular systems of equations
> On 20 Apr 2016, at 13:22, A A via R-help <r-help at r-project.org> wrote: > > > > > I have a situation in R where I would like to find any x (if one exists) that solves the linear system of equations Ax = b, where A is square, sparse, and singular, and b is a vector. Here is some code that mimics my issue with a relatively simple A and b, along with three other methods of solving this system that I found online, two of which give me an error and one of which succ...
2016 Apr 20
0
Solving sparse, singular systems of equations
...matrix into a dense one before doing any linear algebra). Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Apr 20, 2016 at 4:22 AM, A A via R-help <r-help at r-project.org> wrote: > > > > I have a situation in R where I would like to find any x (if one exists) > that solves the linear system of equations Ax = b, where A is square, > sparse, and singular, and b is a vector. Here is some code that mimics my > issue with a relatively simple A and b, along with three other methods of > solving this system that I found online, two of which give me an error and &g...
2005 Feb 02
0
Not reproducing GLS estimates
...("score.1"),direction='long') long\$time<-long\$time-1 Now I run this through a gls as follows: fm1 <- gls(score.1~I(time), data=long, correlation=corAR1(form=~1|ID), method='ML') Now, I am trying to replicate the gls using matrix techniques. Here is my code for to solve (X' V^{-1} X) ^{-1} X' V^{-1} y for the point estimates and (X' V^{-1} X) ^{-1} for the standard errors. score<-long\$score X.mat<-model.matrix(score~time, long, row.names=F) var.mat<-getVarCov(fm1) I<-diag(sample.size) V <- kronecker(I,var.mat) pe<-solve(crossprod(X.m...
2005 Oct 05
2
eliminate t() and %*% using crossprod() and solve(A,b)
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 function that evaluates a quadratic form: quad.form <- function (M, x...
2016 Apr 20
1
Solving sparse, singular systems of equations
...ed file). On Wednesday, April 20, 2016 2:01 PM, Berend Hasselman <bhh at xs4all.nl> wrote: > On 20 Apr 2016, at 13:22, A A via R-help <r-help at r-project.org> wrote: > > > > > I have a situation in R where I would like to find any x (if one exists) that solves the linear system of equations Ax = b, where A is square, sparse, and singular, and b is a vector. Here is some code that mimics my issue with a relatively simple A and b, along with three other methods of solving this system that I found online, two of which give me an error and one of which succ...
2006 Nov 07
4
solve computationally singular
Hi uRsers, when inverting a 2 by 2 matrix using solve, I encountered a error message: solve.default(sigma, tol = 1e-07) : system is computationally singular: reciprocal condition number = 1.7671e-017 and then I test the determinant of this matrix: 6.341393e-06. In my program, I have a condition block that whether a matrix is invertible lik...
2009 Feb 16
2
solve.QP with box and equality constraints
Dear list, I am trying to follow an example that estimates a 2x2 markov transition matrix across several periods from aggregate data using restricted least squares. I seem to be making headway using solve.QP(quadprog) as the unrestricted solution matches the example I am following, and I can specify simple equality and inequality constraints. However, I cannot correctly specify a constraint matrix (Amat) with box constraints per cell and equality constraints that span multiple cells. Namely the solu...
2015 Jan 12
3
[LLVMdev] NP-hard problems in the LLVM optimizer?
Hi all. I’ve heard a couple of times that some of the problems solved by various passes in the optimizer are indeed NP-hard, even though the instances are small enough to be tractable (and very quickly). Is this true? If so, which are these problems? Register allocation? Instruction scheduling? Are they solved exactly or by approximations? Or not solved at all (...
2005 Jan 03
9
Just saw your [Asterisk] xJack Segfault in Asterisk
Hi: Just saw your post while trying to solve a similar asterisk problem. Did not see any responses. Was your problem solved and what was the solution? Carey
2012 Oct 19
2
Which package/function for solving weighted linear least squares with inequality and equality constraints?
Dear All, Which package/function could i use to solve following linear least square problem? A over determined system of linear equations is given. The nnls-function may would be a possibility BUT: The solving is constrained with a inequality that all unknowns are >= 0 and a equality that the sum of all unknowns is 1 The influence of the equatio...
2018 Feb 15
0
Help with factorized argument in solve.QP
Hello David, same problem here with solve.QP. dykstra is causing problems as well and giving for the value NA if factorized = TRUE: library(quadprog) library(Dykstra) R<-cbind(c(1,1),c(0,1)); d<-c(t(R)%*%R%*%c(2,1)) solve.QP(solve(R),d,-as.matrix(c(1,1)),-2,1,factorized = TRUE) S<-t(R)%*%R; solve.QP(S,d,-as.matrix(c(1,...
2001 Oct 18
1
AW: General Matrix Inverse
...************************** ***** > -----Urspr?ngliche Nachricht----- > Von: Torsten Hothorn > Gesendet am: Thursday, October 18, 2001 9:52 AM > An: Philippe Grosjean > Cc: r-help at stat.math.ethz.ch > Betreff: RE: [R] General Matrix Inverse > > > > > I use solve(x) to find the inverse of a matrix (don't know what a > "general > > inverse" is). By the way, what is better: solve(x), qr.solve(x) or > ginv(x)? > > ginv(x) seems to give results for matrices where solve and qr.solve > return > > an error: > > >...
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)  1e+23 > solve(a) Error in solve.default(a) : system is computationally singular: reciprocal condition number = 1e-17 Thanks in advance! Feng -- Feng Li Department of Statistics Stockholm University 106 91 Stockholm, Sweden http://feng.li/ [[alternative HTML version deleted]]
2009 Jul 14
1
LAPACK package
Hi All, Can someone tell me if solve function shown below for my version of R is proper or not? I am using R 2.7.2 .Wherever i have used this function ,i got results which were different from the expected results as computed using SPSS. Description of this function says:-- Solve a System of EquationsDescription This generic functi...