Learning R
MODULE 4.1 Operators and Functions in R
baseR-V2016.2 - Data Management and Manipulation using R
Tested on R versions 3.0.X through 3.3.1
Last update: 15 August 2016
Objectives:
What are some commonly used functions in R?
What operations are performed by:
Basic R functions?
Operators?
Mathematical functions?
Vector functions?
Functions for character strings?
This Module shows examples of many of the more commonly used operators and functions. It is not an exhaustive list.
Let’s begin with …
Some Basic Functions Available in R
Some of the most commonly used functions for dealing with data are:
| Function | Purpose | Function | Purpose |
|---|---|---|---|
| nrow() | No. of rows in object | str() | structure of object |
| ncol() | No. columns in object | class() | var characteristics |
| length() | length of vector | cbind() | bind objects by columns |
| names() | var names in object | rbind() | bind objects by rows |
| ls() | list workspace objects; also | rm() & | remove named objects; |
| ists R Values of functions | rm(list=ls()) | remove all objects |
WARNING!!
rm(list=ls()) removes everything in your current workspace. Objects are permanently removed and no recovery is possible unless you previously saved your objects as a .RData file.
Common Mathematical Operators
Commonly used mathematocal operators for dealing with data are:
| Operator | Function | Operator | Function |
|---|---|---|---|
| + | addition | < and <= | less than (and equal) |
| - | subtraction | > and >= | greater than (and equal) |
| / | division | != | not equal to |
| * | multiplication | == | equal to |
| : | sequence of values | & | and |
| ^ or ** | exponentiation | “|” | or |
Common Mathematical Functions
Commonly used mathematical functions for dealing with data are:
| Operator | Function | Operator | Function |
|---|---|---|---|
| log(x) & log10(x) | log^e & log^10 | cos(x) & acos(x) | cos & arccosine of x |
| sqrt(x) | square root of x | tan(x) & atan(x) | tangent/arctangent of x |
| abs(x) | absolute value of x | floor(x) | integer < x |
| round(x, digits = n) | round x to digits=n | ceiling(x) | integer > x |
| exp(x) | e^x | sin(x) & asin(x) | sin & arcsine of x |
See the CRAN for a complete list.
Basic Vector Functions
Basic Vector functions for dealing with data are:
| Function | Operation | Function | Operation |
|---|---|---|---|
| min(x) & max(x) | min / max of x | range(x) | value range in x |
| sum(x) | sum of all x | colSums(x) | sum of columns in x |
| mean(x) & median(x) | mean and median of x | colMeans(x) | mean of columns in x |
| sd(x) | standard deviation of x | rowSums(x) | sum of rows in x |
| var(x) | sample variance of x | rowMeans(x) | mean of rows in x |
Functions for Character Strings
Basic functions for dealing with character strings are:
| Function | Purpose |
|---|---|
| substr(x, start, stop) | extract from string x characters at location start to location stop |
| paste(x, y, sep = “”) | paste characters in objects x and y together, with no separation |
| tolower(x) | convert characters in x to lower case |
| toupper(x) | convert characters in x to lower case |
| nchar(x) | determine the number of characters in string x, including spaces |