[Gsdesign-commits] r327 - pkg/gsDesign/R

[noreply at r-forge.r-project.org]

Author: keaven
Date: 2011-12-26 16:03:32 +0100 (Mon, 26 Dec 2011)
New Revision: 327

Added:
   pkg/gsDesign/R/nNormal.R
Log:
Added nNormal for 2-sample normal asymptotic sample size.

Added: pkg/gsDesign/R/nNormal.R
===================================================================
--- pkg/gsDesign/R/nNormal.R	                        (rev 0)
+++ pkg/gsDesign/R/nNormal.R	2011-12-26 15:03:32 UTC (rev 327)
@@ -0,0 +1,23 @@
+# sample size for fixed design with 2-arms, normal endpoint, 
+# ratio = randomization ratio
+nNormal<-function(delta1=1,sigma=1.7,sigalt=NULL,alpha=.025,beta=.1,ratio=1,delta0=0)
+{   xi <- ratio/(1+ratio)
+    if(is.null(sigalt)) sigalt <- sigma
+    v <- sigalt^2/xi + sigma^2/(1-xi)
+    theta1 <- (delta1-delta0)/sqrt(v)
+    n <- ((qnorm(alpha)+qnorm(beta))/theta1)^2
+    n
+}
+
+# EXAMPLES
+# equal variances
+n.fix <- nNormal(delta1=.5,sigma=1.1,alpha=.025,beta=.2)
+
+# unequal variances
+
+
+# unequal sample sizes 
+
+
+# non-inferiority
+n.fix <- nNormal(delta1=0,delta0=.5,sigma=1.2)