Displaying 3 results from an estimated 3 matches for "system_of_linear_equ".
2016 Apr 20
0
Solving sparse, singular systems of equations
...; #Error in as(x, "matrix")[i, , drop = drop] : subscript out of boundssolve(qr(A, LAPACK=TRUE),b)
Your code is a mess.
A singular square system of linear equations has an infinity of solutions if a solution exists at all.
How that works you can find here: https://en.wikipedia.org/wiki/System_of_linear_equations
in the section "Matrix solutions".
For your simple example you can do it like this:
library(MASS)
Ag <- ginv(A) # pseudoinverse
xb <- Ag %*% b # minimum norm solution
Aw <- diag(nrow=nrow(Ag)) - Ag %*% A # see the Wikipedia page
w <- runif(3)
z <- xb + Aw %*% w
A...
2016 Apr 20
1
Solving sparse, singular systems of equations
...; #Error in as(x, "matrix")[i, , drop = drop] : subscript out of boundssolve(qr(A, LAPACK=TRUE),b)
Your code is a mess.
A singular square system of linear equations has an infinity of solutions if a solution exists at all.
How that works you can find here: https://en.wikipedia.org/wiki/System_of_linear_equations
in the section "Matrix solutions".
For your simple example you can do it like this:
library(MASS)
Ag <- ginv(A)??? # pseudoinverse
xb <- Ag %*% b # minimum norm solution
Aw <- diag(nrow=nrow(Ag)) - Ag %*% A? # see the Wikipedia page
w <- runif(3)
z <- xb + Aw %*%...
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 succeeds on the