Week 2 from Quizlet

Question 2

control structures in R allow you to…

Answer 2

control the flow of execution of the program

Question 3

if, else

Answer 3

testing a condition

Question 4

for

Answer 4

execute a loop a fixed number of times

Question 5

while

Answer 5

executes a loop while a condition is true

Question 6

repeat

Answer 6

execute an infinite loop

Question 7

break

Answer 7

break the execution of a loop

Question 8

next

Answer 8

skip an interaction of a loop

Question 9

return

Answer 9

exit a function

Question 10

What is a loop index shown as

Answer 10

i

Question 11

loop index

Answer 11

A counter variable used in For / Next loop.

Question 12

seq_len()

Answer 12

Generate regular sequences. and the length

Question 13

seq_along()

Answer 13

Generate regular sequences.

Question 14

subset()

Answer 14

Return subsets of vectors, matrices or data frames which meet conditions.

Question 15

How to stop an infinite loop

Answer 15

break

Question 16

how to skip a part of a loop

Answer 16

next

Question 17

How to tell R to exit a function and return a given value

Answer 17

return

Question 18

what function do you use to construct a function?

Answer 18

function()

Question 19

what do you use to get a standard deviation?

Answer 19

sd()

Question 20

what does na.rm do?

Answer 20

removes NA’s from the object working on

Question 21

how to remove NA’s and calculate the sd of a mydata file

Answer 21

sd(na.rm=TRUE, mydata)

Question 22

What arguments are commonly specified when you call lm()

Answer 22

file, formula, subset,model.

lm(y-x, mydata, 1:100, model=FALSE)

Question 23

what does NULL mean?

Answer 23

There’s nothing there

Question 24

what is the “…” argument?

Answer 24

it indicates a variable number of arguments that are usually passed on to other functions. Often used when extending a function or if arguments can’t be known in advance.

Question 25

Where should you write functions?

Answer 25

in a text file, by choosing “r script” in R

Question 26

How wide should your code be maximum

Answer 26

80 columns of text

Question 27

How to Return subsets of vectors, matrices or data frames which meet conditions.

Answer 27

subset()

Question 28

What is an environment?

Answer 28

a collection of (symbol, value) pairs,

i.e x is a symbol and 3.14 might be its value

Question 29

a function + an enviroment =

Answer 29

a closure or function closure

Question 30

what is the global environment

Answer 30

the workspace

Question 31

what is an empty environment

Answer 31

an environment without a parent

Question 32

What does Lexical Scoping mean?

Answer 32

the values of free variables are searched for in the environment in which the function was defined

Question 33

free variable

Answer 33

variables used in a function that are not local variables nor parameters of that function.

Question 34

How to look at the arguments of a function

Answer 34

ls(environment(function name))

Question 35

How to get the value of an argument in a function, ie n

Answer 35

get(“n”, environment(function name))

Question 36

what class represents the date

Answer 36

Date class

Question 37

what classes represent times

Answer 37

POSIXct class and POSIXlt class

Question 38

how to convert date into a string

Answer 38

as.Date(“yr mnth day”)

Question 39

How to get current time

Answer 39

Sys.time()

Question 40

what function do you use to format how date/time are printed?

Answer 40

strptime()

Question 41

What is an environment in R?

Answer 41

a collection of symbol/value pairs

Question 42

The R language uses what type of scoping rule for resolving free variables?

Answer 42

lexical scoping

Question 43

How are free variables in R functions resolved?

Answer 43

The values of free variables are searched for in the environment in which the function was defined

Question 44

What is one of the consequences of the scoping rules used in R?

Answer 44

All objects must be stored in memory

Question 45

In R, what is the parent frame?

Answer 45

It is the environment in which a function was called