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Section 2: Using R for basic calculations

R has a fairly comprehensive set of mathematical functions and relational operators. This section will show you how to assign a value to a variable as well as how to use R like a scientific calculator.

Mathematical Operations and Vectors

NOTE: Variable names are case sensitive in R, so it is very important to understand that X is not the same as x and Y isn't the same as y.

Figure 2-1

Figure 2-2

Here are a few examples of calculations(with their returned results) that can be performed in R:

10 + 12

[22]

1 + 5 -2/1

[4]

sum(1,2,3,4,5)

[15]

median(1:5)

[3]

This is an example of how creating a C function can perform simple subtraction:

c(2,3,5,7,11,13) - 2

[0 1 3 5 9 11]

Mathmatical Functions

Figure 2-3

Trigonometry(sin,cos and tan) as well as their inverses(asin, acos and atan)

Logarithmic/Exponents(log and exp) and their varients(log1p and expm1)

Assigning Variables

Assigning a variable in R is done by using either <- or =. For example, if we wanted to assign values to x and y, it would appear in R like this:

x <- 5

y = 10

Once these variables are assigned you can use the variables in further calculation:

x + 2 + y -3

[14]

Special Numbers

R has four special numeric values to help with arithmetic:

Inf                          Infinity

-Inf                         Negative Infinity

NaN                       Stands for "Not a Number"

NA                         Placeholder for Missing Values

Classes

All variables in R have a class, which tells you what kinds of variables they are. To find out what class a particular variable pertains to, you can use the code: class(my_variable)

These are the types of classes available within R:

"character"

"complex"

"double"

"expression"

"integer"

"list"

"logical"

"numeric"

"single"

"raw"

Creating a String

The character object is used to represent string values in R. To convert objects into character values we would use the as.character() function.  Here are the string variables in R:

substr(x)

nchar(x)

toupper(x)

tolower(x)

strsplit(x,y)

paste(...)

To create a string in R, you need to first define the variable and relate it to a given function. Then, you specify what data to return when that variable is referenced. Below is an example of a simple string in R that returns randomized capital and lowercase letters as well as numbers using the variable makerandomstring.


Figure 2-4‚Äč