UT2mat: Upper Triangular Vector to Matrix

In fMRItools: Routines for Common fMRI Processing Tasks

Upper Triangular Vector to Matrix

Description

Creates a square matrix from a vector which gives the values for the upper triangle. By default, the vector is expected to include the diagonal values, and the values in the upper triangle are copied to the lower triangle so that the result is symmetric.

Usage

UT2mat(x, diag = "x", LT = "x")

Arguments

x	A vector of values for the upper triangular elements of the desired square matrix.
diag	The values to put on the diagonal, or "x" (default) if x includes the diagonal values.
LT	The values to put on the lower triangle, or "x" (default) to use the upper triangular values such that the result is symmetric. (LT should not contain the diagonal values, which are provided with diag or x).

Value

A square matrix.

Examples

 UT2mat(seq(10)) # defaults: diag="x", LT="x"
 #      [,1] [,2] [,3] [,4]
 # [1,]    1    2    4    7
 # [2,]    2    3    5    8
 # [3,]    4    5    6    9
 # [4,]    7    8    9   10
 UT2mat(seq(3), LT=8)
 #      [,1] [,2]
 # [1,]    1    2
 # [2,]    8    3
 UT2mat(seq(6), diag=0, LT=seq(7,12))
 #      [,1] [,2] [,3] [,4]
 # [1,]    0    1    2    4
 # [2,]    7    0    3    5
 # [3,]    8   10    0    6
 # [4,]    9   11   12    0
UT2mat(rep(-1, 3), diag=c(4,5,6), LT=0)
 #      [,1] [,2] [,3]
 # [1,]    4   -1   -1
 # [2,]    0    5   -1
 # [3,]    0    0    6

fMRItools documentation built on June 10, 2025, 9:09 a.m.