<?xml version="1.0" encoding="utf-8"?><!DOCTYPE article  PUBLIC '-//OASIS//DTD DocBook XML V4.4//EN'  'http://www.docbook.org/xml/4.4/docbookx.dtd'><article><articleinfo><title>FAQ/owanovR</title><revhistory><revision><revnumber>3</revnumber><date>2013-03-08 10:17:30</date><authorinitials>localhost</authorinitials><revremark>converted to 1.6 markup</revremark></revision><revision><revnumber>2</revnumber><date>2008-01-29 16:23:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>1</revnumber><date>2008-01-29 16:21:26</date><authorinitials>PeterWatson</authorinitials></revision></revhistory></articleinfo><section><title>One-way AN(C)OVA in R</title><para>For type I error, alpha, dfgp-1 groups, with dfc covariates to detect a R-squared of size, rsq, wiuth power, pow requires a total sample size of n. </para><para>[COPY AND PASTE INTO R AND ADJUST AS DESIRED] </para><screen><![CDATA[pow <- 0.9
alpha <- 0.05
dfgp <- 4
dfc <- 1
rsq <- 0.1]]></screen><para>[COPY AND PASTE THE BELOW TO OUTPUT N] </para><screen><![CDATA[n <- 2+dfgp+dfc
]]><![CDATA[
fn <- function(n) {
(pow - (1 - pf(abs(qf(1-alpha,dfgp,n-dfgp-dfc-1)),dfgp, 
n-dfgp-dfc-1,ncp=n*rsq/(1-rsq))))
 }
]]><![CDATA[
while (fn(n) > 0) n <- n + 1
print(n)]]></screen></section></article>