# compdist: Comparison Distribution Descriptives In apricom: Tools for the a Priori Comparison of Regression Modelling Strategies

## Description

calculate a comparison distribution and associated descriptive statisics.

## Usage

 `1` ```compdist(a, b, model, output, lambda1, lambda2, trim, strat1, strat2) ```

## Arguments

 `a` a vector containing the sum of square errors or -2 * log likelihood estimates derived using modelling strategy 1. `b` a vector containing the sum of square errors or -2 * log likelihood estimates derived using modelling strategy 2. `model` type of regression model. Either "linear" or "logistic". `output` logical. If output is TRUE the function will return two graphical representations of the comparison distribution. `lambda1` a vector or matrix containing the estimated shrinkage factors derived using strategy 1 `lambda2` a vector or matrix containing the estimated shrinkage factors derived using strategy 2 `trim` logical. If trim is TRUE a "trimmed" comparison distribution will be returned, along with a victory rate and median precision ratio derived using the trimmed distribution. The trimmed distribution only contains precision ratios within a range of plus or minus two times the interquartile range around the median precision ratio. `strat1` a list containing the strategy name and strategy-specific parameter values. `strat2` a list containing the strategy name and strategy-specific parameter values.

## Details

This function works within `compare` to calculate the comparison distribution of strategy 2 against strategy 1. If `trim == TRUE`, a truncated distribution consisting of +/- 2 * interquartile range around the median precision ratio.

The victory rate for linear regression is the left tail probability with a cut-off of 1. The victory rate for logistic regression instead taken at a cut-off of 0. For more details, refer to the accompanying PDF document.

If `output == TRUE` the function will plot a histogram of the distribution and a scatterplot of the precision (SSE or -2 log likelihood) of strategy 2 against strategy 1. Points that lie below the red or blue line represent trials in which strategy 2 outperformed strategy 1 (the victory rate).

## Note

For details of returned values and examples see `compare`.

apricom documentation built on May 29, 2017, 7:36 p.m.