R: Lower and Upper Triangular Part of a Matrix

lower.tri {base} | R Documentation

## Lower and Upper Triangular Part of a Matrix

### Description

Returns a matrix of logicals the same size of a given matrix with entries `TRUE` in the lower or upper triangle.

### Usage

    lower.tri(x, diag = FALSE)
    upper.tri(x, diag = FALSE)

### Arguments

`x` | a matrix or other R object with `length(dim(x)) == 2`. For back compatibility reasons, when the above is not fulfilled, `as.matrix(x)` is called first.
`diag` | logical. Should the diagonal be included?

### See Also

`diag`, `matrix`; further `row` and `col` on which `lower.tri()` and `upper.tri()` are built.

### Examples

    (m2 <- matrix(1:20, 4, 5))
    lower.tri(m2)
    m2[lower.tri(m2)] <- NA
    m2

[Package base version 4.0.5 Index]