R intro(2)

#conditional execution

x <- 2
if (x > 3) print("x<3") else print("x>4")

## [1] "x>4"

x <- 4
if (x < 3) {
    print("x<3")
    z <- "M"
} else {
    print("x>3")
    z <- "F"
}

## [1] "x>3"

z

## [1] "F"

#Iteration,loop

n <- 0
sum.so.far <- 0
while (sum.so.far <= 1000) {
    n <- n + 1
    sum.so.far <- sum.so.far + n
}
print(c(n, sum.so.far))

## [1]   45 1035

sum(1:45)

## [1] 1035

#Apply()

A <- matrix(1:20, 4, 5)
apply(A, 1, sum)  #to every row

## [1] 45 50 55 60

apply(A, 2, sum)  #to ever column

## [1] 10 26 42 58 74

#Writing a new function

my.stat <- function(x) {
    m <- mean(x)
    s <- sd(x)
    res <- list(x = x, m = m, s = s)
    par(mfrow = c(1, 2))
    boxplot(x, main = "Boxplot")
    hist(x, prob = T, col = "lightgray", main = "Histrogram", xlab = "data")
    z <- seq(from = min(x), to = max(x), by = 0.01)
    lines(z, dnorm(z, mean = 3, sd = 1), col = 2, lwd = 3, lty = 2)
}
data <- rnorm(1000, mean = 3, sd = 1)
my.stat(x = data)