# ldboundary: Linear Discriminant Boundary In phonTools: Tools for Phonetic and Acoustic Analyses

## Description

Given two mean vectors and a covariance matrix (and optional prior probabilities), this function will return the slope and intercept of the boundary line between the two categories.

## Usage

 `1` ```ldboundary (mean1, mean2, covariance, prior1 = .5, prior2 = .5, add = F, ...) ```

## Arguments

 `mean1` A mean vector for category 1, must contain 2 elements. `mean2` A mean vector for category 2, must contain 2 elements. `covariance` A 2x2 covariance matrix for both distributions. `prior1` The prior probability of category 1. `prior2` The prior probability of category 2. `add` If TRUE, the boundary line is added top the plot. `...` Additional parameters are passed to the internal call of the line plotting function, in the event that add = T.

## Value

The slope and intercept of the boundary line are returned.

## Author(s)

Santiago Barreda <sbarreda@ucdavis.edu>

## References

http://en.wikipedia.org/wiki/Linear_discriminant_analysis https://onlinecourses.science.psu.edu/stat557/book/export/html/35

## Examples

 ```1 2 3 4 5 6 7 8 9``` ```## create two groups with the same covariance patterns group1 = rmvtnorm (200, means= c(0,0), k=2, sigma = -.4) group2 = rmvtnorm (200, means= c(3,3), k=2, sigma = -.4) covariance = (var (group1) + var (group2)) / 2 ## plot groups and boundary line between categories. plot (group1, col = 2, pch = 16, ylim = c(-2,5), xlim = c(-2,5)) points (group2, col = 4, pch = 16) ldboundary (c(0,0), c(3,3), covariance, add = TRUE) ```

phonTools documentation built on May 1, 2019, 6:26 p.m.