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Keep the lower or upper triangle of a matrix

Source: R/FUNCTIONS_MATRIX.R
matrix_triangle.Rd

Keeps one triangle of a matrix, including the diagonal, and fills the other triangle with the value of off_diagonal; optionally replaces the diagonal. Useful for displaying correlation or covariance matrices without repeated values.

Usage

matrix_triangle(m, off_diagonal = NA, diagonal = NULL, type = "lower")

Arguments

m

A numeric matrix, or an object that as.matrix() turns into a numeric matrix (e.g. a data frame of numbers).

off_diagonal

Value used to fill the dropped triangle. Default NA.

diagonal

Value(s) to place on the diagonal: a single value or one value per diagonal element. If NULL (default), the original diagonal is kept.

type

Character, "lower" (default) or "upper": the triangle to keep.

Value

A numeric matrix with the same dimensions and row / column names as m.

See also

display_upper_lower_triangle, symmetric_matrix

Examples

m<-matrix(1:9,nrow=3,ncol=3)
matrix_triangle(m=m)
#>      [,1] [,2] [,3]
#> [1,]    1   NA   NA
#> [2,]    2    5   NA
#> [3,]    3    6    9
matrix_triangle(m=m,diagonal=NA,type="lower")
#>      [,1] [,2] [,3]
#> [1,]   NA   NA   NA
#> [2,]    2   NA   NA
#> [3,]    3    6   NA
matrix_triangle(m=m,diagonal=NULL,type="lower")
#>      [,1] [,2] [,3]
#> [1,]    1   NA   NA
#> [2,]    2    5   NA
#> [3,]    3    6    9
matrix_triangle(m=m,diagonal=NA,type="upper")
#>      [,1] [,2] [,3]
#> [1,]   NA    4    7
#> [2,]   NA   NA    8
#> [3,]   NA   NA   NA
matrix_triangle(m=m,diagonal=NULL,type="upper")
#>      [,1] [,2] [,3]
#> [1,]    1    4    7
#> [2,]   NA    5    8
#> [3,]   NA   NA    9