Make a square matrix symmetric by averaging.

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Description

Matrix symmetry might depend on numerical precision issues. The older version of JAGS had a bug related to this issue for multivariate normal nodes. This simple function can fix the issue, but new JAGS versions do not require such intervention.

Usage

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Arguments

x

A square matrix.

Details

The function takes the average as (x[i, j] + x[j, i]) / 2 for each off diagonal cells.

Value

A symmetric square matrix.

Note

The function works for any matrix, even for those not intended to be symmetric.

Author(s)

Peter Solymos, solymos@ualberta.ca

Examples

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x <- as.matrix(as.dist(matrix(1:25, 5, 5)))
diag(x) <- 100
x[lower.tri(x)] <- x[lower.tri(x)] - 0.1
x[upper.tri(x)] <- x[upper.tri(x)] + 0.1
x
make.symmetric(x)

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