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Lower/Upper Triangle Elements of a Matrix

Tri2M.Rd

Lower/Upper triangle elements of a matrix or forms a matrix from a vector of lower/upper triangle elements

Usage

Tri2M(x, lower.tri = TRUE, reverse = TRUE, diag = TRUE)

Arguments

x

Matrix or vector

lower.tri

If x is a matrix then the lower triangle (TRUE) or upper triangle FALSE elements (including diagonal elements) are returned. If x is a vector a matrix is formed under the assumption that x are the lower triangle (TRUE) or upper triangle (FALSE) elements.

reverse

logical: ifTRUE a symmetric matrix is formed, if FALSE the remaining triangle is left as zeros.

diag

logical: ifTRUE diagonal elements are included.

Value

numeric or matrix

Author

Jarrod Hadfield j.hadfield@ed.ac.uk

Examples

M<-rIW(diag(3), 10)
x<-Tri2M(M)
x
#> [1]  0.8807261  0.6250442 -0.3006476  6.0801571  0.7062031  1.8132052
Tri2M(x, reverse=TRUE)
#>            [,1]      [,2]       [,3]
#> [1,]  0.8807261 0.6250442 -0.3006476
#> [2,]  0.6250442 6.0801571  0.7062031
#> [3,] -0.3006476 0.7062031  1.8132052
Tri2M(x, reverse=FALSE)
#>            [,1]      [,2]     [,3]
#> [1,]  0.8807261 0.0000000 0.000000
#> [2,]  0.6250442 6.0801571 0.000000
#> [3,] -0.3006476 0.7062031 1.813205