Generate a tridiagonal matrix.

Generate a tridiagonal matrix with upperDiag as superdiagonal, lowerDiag as subdiagonal and mainDiag as diagonal.

tridiag(mainDiag, upperDiag, lowerDiag)

Arguments

mainDiag	Diagonal of tridiagonal matrix.
upperDiag	Superdiagonal of tridiagonal matrix. Must have length length(mainDiag) - 1.
lowerDiag	Subdiagonal of tridiagonal matrix. Must have length length(mainDiag) - 1.

Value

Tridiagonal matrix.

Examples

set.seed(987)
mainDiag <- sample(100:110, size = 6, replace = TRUE)
upperDiag <- sample(10:20, size = 5, replace = TRUE)
lowerDiag <- sample(1:10, size = 5, replace = TRUE)

tridiag(mainDiag, upperDiag, lowerDiag)
#>      [,1] [,2] [,3] [,4] [,5] [,6]
#> [1,]  105   14    0    0    0    0
#> [2,]    4  110   13    0    0    0
#> [3,]    0    2  106   19    0    0
#> [4,]    0    0    4  106   17    0
#> [5,]    0    0    0    2  108   12
#> [6,]    0    0    0    0    7  102