Given:
h_i=t_(i+1)-t_i for i=1,...,n-1 where n is a positive integer.
The matrix Q is an n by (n-2) matrix with entries q_(i,j) with i=1,...,n and j=2,...n-1 given by:
矩阵Q是n×(n-2)矩阵,条目q_(i,j),其中i = 1,...,n和j = 2,... n-1由下式给出:
q_(j-1,j)=1/h_(j-1)
q_(j,j)=-(1/h_(j-1)+1/h_j)
q_(j+1,j)=1/h_j
q_(i,j)=0 for |i-j|>=2
I want to get a matrix Q. How do i write a program for this matrix in R? Many thanx in advance.
我想得到一个矩阵Q.我如何在R中为这个矩阵编写一个程序?很多人提前。
1 个解决方案
#1
1
If I've figured out the subscripts correctly, I think this will do it:
如果我已经正确地找出了下标,我想这会做到:
n <- 100
t <- sort(runif(n))
h <- diff(t)
Q <- matrix(0,n,n-2)
Q[row(Q)==col(Q)-1] <- 1/h[1:(n-3)]
Q[row(Q)==col(Q)+1] <- 1/h[1:(n-2)]
diag(Q) <- c(NA,-1/h[1:(n-3)] - 1/h[2:(n-2)])
#1
1
If I've figured out the subscripts correctly, I think this will do it:
如果我已经正确地找出了下标,我想这会做到:
n <- 100
t <- sort(runif(n))
h <- diff(t)
Q <- matrix(0,n,n-2)
Q[row(Q)==col(Q)-1] <- 1/h[1:(n-3)]
Q[row(Q)==col(Q)+1] <- 1/h[1:(n-2)]
diag(Q) <- c(NA,-1/h[1:(n-3)] - 1/h[2:(n-2)])