--- title: "Standard scores" author: "Tera Letzring" date: "September 2017" output: html_document --- ```{r setup, include=FALSE} knitr::opts_chunk$set(echo = TRUE) ``` ```{r set wd and read in data} #set the working directory (wd) to the folder that contains the script file, and read in the data x <- getwd() setwd(x) SDdata = read.table("schooldays.csv", header=T, sep=",") head(SDdata) attach(SDdata) ``` ```{r standard scores} #create z-scores and add new variable to existing data frame. center = TRUE subtracts the mean, scale = TRUE divides by standard deviation SDdata$Zscores <- scale (absent, center = TRUE, scale = TRUE) mean(SDdata$Zscores) sd(SDdata$Zscores) #create T-scores and add to existing data frame SDdata$Tscores <- 50 + (10*SDdata$Zscores) mean(SDdata$Tscores) sd(SDdata$Tscores) #output the first 6 rows of the schooldays data set head(SDdata) ```