R exploration for week 3

w3 <- read.table("../stats1/Stats1.13.HW.03.txt", header = T)

par(mfrow = c(4, 2))

w3Variates <- names(w3)[sapply(c(1, 3, 2, 4, 5, 7, 6, 8), function(x) {
    x + 2
})]

for (name in w3Variates) {
    hist(w3[, name], main = name)
}

plotW3 <- function(x) {
    hist(w3[, x], main = x)
}
x <- lapply(w3Variates, plotW3)

w3Names <- names(w3)[3:10]
as.string(w3Names[[1]])

## Error: could not find function "as.string"

names(w3)[sapply(c(1, 3, 2, 4, 5, 7, 6, 8), function(x) {
    x + 2
})]

## [1] "S1.pre"  "S1.post" "S2.pre"  "S2.post" "V1.pre"  "V1.post" "V2.pre" 
## [8] "V2.post"

var(w3$S1.pre)

## [1] 7.837

par(mfrow = c(1, 2))
barplot(sapply(w3, var, USE.NAMES = T)[w3Variates], main = "Variances")
barplot(sapply(w3, mean, USE.NAMES = T)[w3Variates], main = "Mean")

## Warning: argument is not numeric or logical: returning NA

myDf <- data.frame(names = c("Variances", "Means", "Standard Deviation"), f = c("var", 
    "mean", "sd"))
myDfPlot <- function(row) {
    f <- get(as.character(row$f))
    barplot(sapply(w3, f, USE.NAMES = T)[w3Variates], main = row$names)
}
par(mfrow = c(2, 2))
x <- by(myDf, 1:nrow(myDf), myDfPlot)

## Warning: argument is not numeric or logical: returning NA

mean(w3$S1.pre)

## [1] 18.16

sum(w3$S1.pre)/length(w3$S1.pre)

## [1] 18.16