On 30-11-2013, at 08:37, Loyack, Eric <eloy...@arcadia.edu> wrote: > I am using R Studio and writing code to determine p-values for statistical > t-tests. Code is below. When I print out the values in the loop for > PTMpvalMeans they are correct, but when I store them the 10th one > overwrites the 11th. Can someone tell me what I am doing wrong? Thanks in > advance, Eric >
R FAQ 7.31 (http://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f) Insert print(formatC(10*rho+1,digits=16,format="f")) before the line with print(PTMpvalMeans[rho*10 + 1]) in your code and you should see what’s wrong. Use an explicit counter variable k and increment with k <- k+1 to index your vectors. Berend > rho <- 0.0 > PTMpvalMeans <- numeric(11) > while (rho < 1.0){ > x1 <- rnorm(25,0,1) > x2 <- rnorm(25,0,1) > y1 <- rnorm(25,0,1) > y2 <- rnorm(25,0,1) > w1 <- rho*x1 + sqrt(1-rho^2)*y1 > w2 <- rho*x2 + sqrt(1-rho^2)*y2 > controlPretest <- 50 + 10*x1 > groupPretest <- 50 + 10*x2 > controlPosttest <- 60 + 10*w1 > groupPosttest <- 70 + 10*w2 > postTestMethod <- > t.test(controlPosttest,groupPosttest,mu=0,alternative="two.sided") > PTMpval <- postTestMethod$p.value > for (i in 1:999){ > x1 <- rnorm(25,0,1) > x2 <- rnorm(25,0,1) > y1 <- rnorm(25,0,1) > y2 <- rnorm(25,0,1) > w1 <- rho*x1 + sqrt(1-rho^2)*y1 > w2 <- rho*x2 + sqrt(1-rho^2)*y2 > controlPretestLoop <- 50 + 10*x1 > groupPretestLoop <- 50 + 10*x2 > controlPosttestLoop <- 60 + 10*w1 > groupPosttestLoop <- 70 + 10*w2 > controlPretest <- c(controlPretest,controlPretestLoop) > groupPosttest <- c(groupPosttest,groupPosttestLoop) > groupPretest <- c(groupPretest,groupPretestLoop) > controlPosttest <- c(controlPosttest,controlPosttestLoop) > postTestMethodLoop <- > t.test(controlPosttestLoop,groupPosttestLoop,mu=0,alternative="two.sided") > PTMpvalLoop <- postTestMethodLoop$p.value > PTMpval <- c(PTMpval,PTMpvalLoop) > } > PTMpvalMeans[rho*10 + 1] <- mean(PTMpval) > print(rho) > print(PTMpvalMeans[rho*10 + 1]) > rho <- rho + 0.1 > } > PTMpvalMeans > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
