# Operators reference

 `-` Minus, can be unary or binary `+` Plus, can be unary or binary `!` Unary not `~` Tilde, used for model formulae, can be either unary or binary `?` Help `:` Sequence, binary (in model formulae: interaction) `*` Multiplication, binary `/` Division, binary `^` Exponentiation, binary `%x%` Special binary operators, x can be replaced by any valid name `%%` Modulus, binary `%/%` Integer divide, binary `%*%` Matrix product, binary `%o%` Outer product, binary `%x%` Kronecker product, binary `%in%` Matching operator, binary (in model formulae: nesting) `<` Less than, binary `>` Greater than, binary `==` Equal to, binary `>=` Greater than or equal to, binary `<=` Less than or equal to, binary `&` And, binary, vectorized `&&` And, binary, not vectorized `|` Or, binary, vectorized `||` Or, binary, not vectorized `<-` Left assignment, binary `->` Right assignment, binary `\$` List subset, binary

# Quotes reference

```````a + b` <- 3
`:)` <- "smile"
`    ` <- "spaces"
ls()
`:)```````
`````` "    "  ":)"    "a + b"
 "smile"
``````

You can also create non-syntactic bindings using single and double quotes instead of backticks, but I don’t recommend it. The ability to use strings on the left hand side of the assignment arrow is a historical artifact, used before R supported backticks.

# Assignment: `<-` and `<<-`reference

• `<-` always creates a variable in the current environment.
• `<<-` never creates a variable in the current environment, but instead modifies an existing variable found by walking up the parent environments.
• If `<<-` doesn’t find an existing variable, it will create one in the global environment.

# Access the value of last evaluated expression howto

• Use `.Last.value`
``````10
.Last.value``````
`````` 10
 10
``````