Chapter 1 Variables, Math, and Comparisons

1.1 Help

# Hi. This is a comment.

# If you know a function's name, but not how to use it:
?t.test

You can also click a function and press F1 to see the help page.

If you don’t know the exact name of a function or variable, you can type part of the name and press tab to autocomplete and see some info about it.

1.2 Assignment

a = 6
b = 8
c = 5.44
d = TRUE
e = "hello world" 
e = 'hello world' # same as double quote

Note: No semicolon or “var” needed

You’ll sometimes see a <- 6 instead of a = 6. Just use =. Some people insist on using <-. They are silly.

1.3 Names with weird characters

R allows names to have a ., and it’s common in many built-in functions. For your own variables, avoid it if possible. If you want to have a space in a name, use an underscore (_) instead of being ridiculous.

To learn how to access object members, see the lists chapter.

this.is.a.variable.name = 1
better_name = 2

You can use any weird character like a space in a variable name by surrounding the name with `. Avoid it if you can, but sometimes it’s necessary when you load data from a file.

`more than four (>4)` = 5

1.4 Console Output

Print a in the console

#> [1] 6

The [1] is output because it is the first element in an array. For more info, see the arrays chapter.

Another option that’s useful inside functions, which don’t output most results

print(a)

#> [1] 6

1.5 Math

Arithmetic

z = a + b
z = a - b
z = a * b
z = a / b
z = a %/% b # Integer division
z = a %% b # Note the double % for the modulo operator
z = a ^ b # exponent

1 + 2 - 3 * 4 / 5 ^ 6 # Please excuse my dear aunt, Sally

#> [1] 2.999232

Note: There is no ++ or +=

Functions for floats

floor(4.82)

#> [1] 4

ceiling(4.82)

#> [1] 5

Rounding

round(4.4) # round down

#> [1] 4

round(4.6) # round up

#> [1] 5

round(4.5) # round to even (down)

#> [1] 4

round(5.5) # round to even (up)

#> [1] 6

Other basic math functions

sin(pi/2) + cos(0) # radians, not degrees

#> [1] 2

log(exp(2)) # base e (like ln) is the default

#> [1] 2

log(100, 10) # use base 10

#> [1] 2

1.6 Comparisons

a == b

#> [1] FALSE

a != b

#> [1] TRUE

a > b

#> [1] FALSE

a < b

#> [1] TRUE

a >= b

#> [1] FALSE

a <= b

#> [1] TRUE

1.7 Boolean

TRUE & FALSE

#> [1] FALSE

TRUE | FALSE

#> [1] TRUE

!TRUE

#> [1] FALSE

There’s & and &&. You usually want just &.