Basic functions

Try out a few common, basic functions to learn what they do and how they work:

Square root: sqrt(64) (you could also do this: 64^0.5)
Exponential: exp(0), exp(1), exp(-10),
Natural log: log(10), log(1), log(0), log(-1), log(exp(2))
Factorial: factorial(1), factorial(5), factorial(-1), factorial(0)
Round: round(3.1415), round(3.1415, digits=2)
Absolute value: abs(-1), abs(1)

Here’s a couple more to foreshadow where we’ll be going:

Type rep("hello!", 100) and take a look at the output. What does rep() do?
Type hist(x=rnorm(300)) and see what happens. What do you think the hist() function does? What about the rnorm() function? How could you find out more about each function?

Objects

Make some objects using the following assignments:

w <- 1
x <- 1
y <- 2
z <- 3

Using only these objects, try writing code to answer the following questions:

Write a statement comparing the magnitude of z to w that returns TRUE
Write a statement comparing the magnitude of x to w that returns TRUE
Fill in the correct relational operators to make this statement return TRUE: (x __ y) & (z __ y)

Try answering some of these questions before running any code - reason through the commands, then run the code and see if you were correct:

What happens when you try to do math with a string: "3" / 4
What do you think R will return if we divide infinity by a really big number: Inf / 10^20
Why doesn’t the following code return TRUE (Hint: read ahead to find out):

(0.1 + 0.2) == 0.3

## [1] FALSE

Page sources:

Some content on this page has been modified from other courses, including:

EMSE 6574, Sec. 11: Programming for Analytics (Fall 2019)
George Washington University | School of Engineering & Applied Science
Dr. John Paul Helveston | jph@gwu.edu | Mondays | 6:10–8:40 PM | Phillips Hall 108 | |
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