Printing



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pi



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sqrt(2)



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print(pi)
print(sqrt(2))



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print(matrix(c(1, 2, 3, 4), 2, 2))



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print(list("a", "b", "c"))

`cat` function

It allows you to cat multiple items. Limitation is it cannot print compound data like list and matrix.



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fib <- c(1, 1, 2, 3, 5)
cat("The fist 5 Fibonaci number is: ", fib, "...\n")



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# cat(list("a", "b", "c"))
# cat(matrix(c(1, 2, 3, 4), 2, 2))



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x <- 3



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x <- c("fee", "fie", "foo", "fun")
print(x)



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x <- 10
y <- 50
z <- c("three", "blind", "mice")
f <- function(n, p) sqrt(p/n)
ls()



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ls.str()



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.hidvar <- 10
ls()



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ls(all.names = TRUE)



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x <- 2 * pi
x



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rm(x)
ls()



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c(1, 1, 2, 3, 5, 8, 13, 21)



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v1 <- c(1, 2, 3)
v2 <- c("A", "B", "C")
v3 <- c(v1, v2)



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print(v3)



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print(mode(v1))
print(mode(v2))
print(mode(v3))

When combine two vectors, they will be flaten and combined to a single one
If they are different types, R will try to convert them to the same type as in the above example.



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x <- c(0, 1, 1, 2, 3, 5, 8, 13, 21, 34)



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mean(x)



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median(x)



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sd(x)



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var(x)



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y <- log(1+x)



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cor(x, y)



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cov(x, y)



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x <- c(0, 1, 1, 2, 3, NA)
mean(x)
sd(x)



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mean(x, na.rm = TRUE)



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sd(x, na.rm = TRUE)



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str(mtcars)



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dframe <- mtcars[c("mpg", "drat", "wt")]



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str(dframe)
# print(dframe)
colMeans(dframe)



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lapply(dframe, mean)



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lapply(dframe, sd)



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var(dframe)



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1:5



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seq(from = 1, to = 5, by = 2)



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rep(x = 1, times = 5)



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0:9
10:19
9:0



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seq(from = 0, to = 20, by = 2)



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seq(from = 0, to = 20, by = 5)



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seq(from = 0, to = 20, length.out = 5)



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seq(from = 0, to = 100, length.out = 5)



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seq(from = 0, to = 1.0, length.out = 5)



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rep(pi, times = 5)



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a <- 3
a == pi



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a != pi



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a < pi



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a > pi



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a <= pi



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a >= pi



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v <- c(3, pi, 4)
w <- rep(pi, times = 3)
v < w



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v <= w



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v > w



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any(v == pi)



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all(v > 0)



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all(v == 0)



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years <- c(1960, 1964, 1970, 1994)



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names(years) <- c("Kenndey", "Johnson", "Carter", "Clinton")



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years



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years[c("Kenndey", "Clinton")]



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fib <- c(0, 1, 1, 2, 3, 5, 8, 13, 21)



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fib[1]; fib[2]



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fib[1:3]



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fib[c(1, 2, 4, 8)]; fib[-(1:3)]; fib[-c(1, 2, 4, 8)]



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fib < 10; fib[fib < 10]



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fib %% 2 == 0; fib[fib %% 2 == 0]



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fib > median(fib); fib[fib > median(fib)]



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fib < quantile(fib, 0.26); fib[fib < quantile(fib, 0.26)]



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v <- c(11, 12, 13, 14, 15)
w <- 1:5



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v+w; v - w; v*w; v/w



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w; w+2; w-2; w*2; w/2; w^2; 2^w



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w; w - mean(w); sd(w); (w - mean(w)) / sd(w)



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