triMatInd | R Documentation |

This function outputs the indices of one triangle (the lower one by default) of an input square matrix. It is used by `simMat`

and, for large matrices, makes it faster than e.g. with `lower.tri`

or `upper.tri`

.

triMatInd(mat, lower = TRUE, list = FALSE)

`mat` |
a square matrix. |

`lower` |
logical indicating whether the indices should correspond to the lower triangle. The default is TRUE; FALSE produces the upper triangle indices. |

`list` |
logical indicating whether the results should be output as a list instead of a matrix. The default is FALSE. |

The indices (row, column) of the elements of the matrix that belong to the requested triangle.

A. Marcia Barbosa

http://stackoverflow.com/questions/20898684/how-to-efficiently-generate-lower-triangle-indices-of-a-symmetric-matrix

`lower.tri`

, `upper.tri`

mat <- matrix(nrow = 4, ncol = 4) mat triMatInd(mat) triMatInd(mat, list = TRUE)

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