parcor {ggm}

Partial correlations

Description

Finds the matrix of the partial correlations between pairs of variables given the rest.

Usage

parcor(S)

Arguments

S

a symmetric positive definite matrix, representing a covariance matrix.

Details

The algorithm computes - \sigma^{rs}/(\sigma^{rr} \sigma^{ss})^{1/2} where the \sigma^{rs} are concentrations, i.e. elements of the inverse covariance matrix.

Value

A symmetric matrix with ones along the diagonal and in position (r,s) the partial correlation between variables r and s given all the remaining variables.

Author(s)

Giovanni M. Marchetti

References

Cox, D. R. & Wermuth, N. (1996). Multivariate dependencies. London: Chapman & Hall.

See Also

var, cor, correlations

Examples

### Partial correlations for the mathematics marks data
data(marks)
S <- var(marks)
parcor(S)