R - Lab 1

Question 1

text

Answer 1

Makes a comment.

Use comments frequently

Question 2

3+5

Answer 2

Addition

8

Question 3

2*3

Answer 3

Multiplication

6

Question 4

4^2

Answer 4

Exponents

16

Question 5

exp(1.5)

Answer 5

Calculates e to the 1.5 power

Question 6

x=exp(1.5)

Answer 6

Makes variable ‘x’ equal to exp(1.5)

Doesn’t report anything

Question 7

Recalling a variable

Answer 7

Type the variable
Ex: If x=exp(1.5)
x
4.481689

Question 8

log(x)

Answer 8

Natural log of x

Question 9

What happens if you write incomplete code?
Example:
x=exp(1.5

Answer 9

R will give a ‘+’ on the next line

- Either finish (type ‘)’ ) or press escape

Question 10

How to scroll through history of commands?

Answer 10

Up and down arrows

Question 11

How to bring up the help file for a command?

Answer 11

help([command])

So:
help(exp)

Question 12

How to search for functions that include a certain word?

Answer 12

??’[text]’

??’exponentiate’

Question 13

What letter must you put in front of parenthesis to create a vector (list of values)?

Answer 13

c

Question 14

Example vector

Answer 14

x=c(4,5,6)

Question 15

In vectors:

x[2]

Answer 15

Tells us the 2nd value of x.

If
x=c(4,5,6)
Then
x[2]= 5

Question 16

What will exp(x) do if x contains a vector?

Answer 16

Calculate exp to the power of each value in x; return a list of scalars.

Question 17

What is a function?

Answer 17

Any command that takes arguments (in parentheses) and returns results based on a calculation.

Question 18

Example functions

Answer 18

log(x)

exp(x)

Question 19

What is a matrix?

Answer 19

A block of numbers with multiple rows and columns.

Question 20

How to create a matrix in R?

Answer 20

1. Create at least two vectors.
   Ex:
   year=c(1800,1850,1900,1950)
   carbon=c(8,54,534,1630)
2. Assign the data.frame() function to a variable.
   Ex:
   datum=data.frame(Year=year,Carbon=carbon)
3. View by typing the variable
   Ex:
   datum shows the matrix
   datum[2] shows just the second column

Question 21

How do you show the data of just a column AS a column? How do you show the data of a column AS a row of text?

Answer 21

Column
datum[2]

Row of text
datum$Carbon

Question 22

What are the three easy summaries/analyses of data?

Answer 22

summary(datum)
- provides mean and quartile

head(datum)
[SAYS ‘checks that data was imported properly’ but seems like python head()]

names(datum)
Gives you attributes of data or other objects

Question 23

How do you make a simple plot?

Answer 23

plot(datum)

X-axis is the first variable in the matrix

Question 24

plot(Carbon~Year) doesn’t work. Why?

Answer 24

‘Carbon’ and ‘Year’ don’t exist outside the datum data.frame

Question 25

If you can’t reference the column names outside of the dataframe, how do you plot it?

Answer 25

plot(Carbon~Year,data=datum)

Question 26

Another way of doing plots

Answer 26

plot(x=datum$Year,y=datum$Carbon)

Question 27

How do you clear console, and does it eliminate objects you’ve created?

Answer 27

“Edit” option in top left > “Clear Console”

This does NOT eliminate the objects you created.

Question 28

How do you list all the objects in memory?

Answer 28

ls()

Think “list”

Question 29

How do you remove objects in memory?

Answer 29

rm()

Question 30

How do you load a package? What’s a prerequisite?

Answer 30

Pre: Package is installed. Giggidy.

Ex:
library(nlme)

Question 31

What is the code to load data into R?

Answer 31

datum=read.csv(file.choose())