02 the r language part 1

7/24/2019 02 the R Language Part 1

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Garrett Grolemund

Master Instructor, RStudio

August 2014

The R Language (1 of 2)Understand how R storesand works with data
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1. RStudio basics

2. R basics

3. Data structures

4. Data types

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RStudio


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Studio

Open RStudio as you would any program. It'sicon looks like this

Getting started



Studio

The RStudio window is divided into 3-4 panes

Each keeps track of separate information.



Studio

The console gives

you a place to

execute commands

written in the R

computer language

R Console



Studio

Type commands on

the line that begins

with a > sign (known

as the prompt)

Command

prompt



Studio

When you hit enter,

RStudio will run

your command and

display any outputbelow it

Output

OutputNew prompt


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Studio

As you enter

commands, you

accumulate a

history of pastcommands

History

d


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Studio

[1]

R displays an index

next to the output.

Just ignore this.

Somewhat helpfulwhen R returns more

than one value in the

output.

S di


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Studio

5 + 5

# 10

4 - 1

# 3

1 * 2

# 2

4 ^ 2

# 16

R

R is like a fancy calculato

on your computer

S di


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Studio

a


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round(3.1415)

# 3

factorial(3)

# 6

sqrt(9)

# 3

R

And it has functions that

you do more sophisticate

manipulations

3! = 3 x 2

square ro


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Your turn

What do you think this will return?

You have 30 seconds.

factorial(round(3.1415) + 1)


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Your turn

What do you think this will return?

You have 30 seconds.


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factorial(2 + 1)

factorial(3)

6

R always works from the innermost parenthesi

the outermost (just like a calculator).

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factorial(round(2.0015)+ 1)

factorial(2+ 1)

factorial(3)

6



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factorial(2 + 1)

factorial(3)

6



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factorial(2 + 1)

factorial(3)

63! = 3 x 2 x 1



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+ prompt

If your prompt turns

into a "+", R thinks

you haven't finished

your previous

command.Either finish the

command, or press

escape.

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+ prompt

If your prompt turns

into a "+", R thinks

you haven't finished

your previous

command.Either finish the

command, or press

escape.


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Your turn

Open RStudio and try the following tasks:

1. Pick a number and add 2 to it

2. Multiply the result by 3

3. Subtract 6 from the result of step 24. Divide the result of step 3 by 3

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10 + 2

# 12

12 * 3

# 36

36 - 6

# 30

30 / 3

# 10


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Workflow

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R scripts

It is easier to compose your code in an Rscript than in the command line.

To open an R script, go to File>New File>R

Script in the toolbar.


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R Script pane


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1.Write code in an R

script

Common

workflow


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script

2.Run code in

console with Run

Common

workflow


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script

2.Run code in

console with Run3.Save R Script

when finished

Common

workflow


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Shortcuts


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[]


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[Tab]


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[Cmd + ]


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[Cmd + enter]


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R objects

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foo


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foo


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foo


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foo


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When you create an R object, you'll see it appe

in your workspace pane

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foo


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a

b

FOO

my_var

.day

Object names

Object names cannot begin with numbers.

Wise to avoid names already in use.

1trial

$

^mean

2nd

!bad

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a

b

sum

Capitalization matters

R will treat each of these as a di"erent

object

A

B

SUM

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foo

# 4

rm(foo)

foo

# Error: object 'foo' not found

rm

You can remove an object with rm

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This can be useful if you overwrite an object that

comes with R

pi# 3.141593

pi


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Data

structures

W


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Warm up

Look at the R object WorldPhones(by

typing its name in the console).

What is inside of WorldPhones?

WorldPhones


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N.Amer Europe Asia S.Amer Oceania Africa Mid.Amer

1951 45939 21574 2876 1815 1646 89 555

1956 60423 29990 4708 2568 2366 1411 733

1957 64721 32510 5230 2695 2526 1546 773

1958 68484 35218 6662 2845 2691 1663 836

1959 71799 37598 6856 3000 2868 1769 911

1960 76036 40341 8220 3145 3054 1905 1008

1961 79831 43173 9053 3338 3224 2005 1076

WorldPhones

You can save more than a single number in an

object by creating a vector,matrix, orarray.

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vec


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vec


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mat


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mat


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matrix(c(1, 2, 3, 4, 5, 6), nrow = 2)

# [,1] [,2] [,3]

# [1,] 1 3 5

# [2,] 2 4 6

vector of elements to

go in the matrix

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matrix(c(1, 2, 3, 4, 5, 6), nrow = 2)

# [,1] [,2] [,3]

# [1,] 1 3 5

# [2,] 2 4 6

number of rows for

matrix

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matrix(c(1, 2, 3, 4, 5, 6), nrow = 3)

# [,1] [,2]

# [1,] 1 4

# [2,] 2 5

# [3,] 3 6

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vec + 4

# 5 6 7 14 104

vec * 4

# 4 8 12 40 400

vec * vec

# 1 4 9 100 10000

Math: element-wise

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vec * vec

# 1 4 9 100 10000

vec

1

2

3

10

100

vec

1

2

3

10

100

1

4

9

100

10000

*

*

*

*

*

=

=

=

=

=

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vec %*% vec # inner

# [,1]

# [1,] 10114

vec %o% vec # outer

# [,1] [,2] [,3] [,4] [,5]

# [1,] 1 2 3 10 100

# [2,] 2 4 6 20 200

# [3,] 3 6 9 30 300

# [4,] 10 20 30 100 1000

# [5,] 100 200 300 1000 10000

Matrix multiplication

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mat

# [,1] [,2] [,3]

# [1,] 1 3 5

# [2,] 2 4 6

t(mat)

# [,1] [,2]

# [1,] 1 2

# [2,] 3 4

# [3,] 5 6

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array(c(1, 2, 3, 4, 5, 6), dim = c(2, 2, 3

arrays

Combine multiple elements into an array

that has three or more dimensions.

Create with the arrayfunction.

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array(c(1, 2, 3, 4, 5, 6), dim = c(2, 2, 3

arrays

Combine multiple elements into an array

that has three or more dimensions.

Create with the arrayfunction.

Wewo

o


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Data types

Warm up


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Wha

ttyp

esofd

inthi

sspr

d t t

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data t esLike Excel, Numbers, etc., R can recognize

di"erent types of data.

We'll look at four basic types:

# numbers

# character strings (text)

# logical

# factor

numeric

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numeric

Any number, no quotes.

Appropriate for math.

1 + 1

3000000

class(0.00001)

# "numeric"

character

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character

Any symbols surrounded by quotes.

Appropriate for words, variable names,

messages, any text.

"hello"

class("hello")

# "character"

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"hello" + "world"

# Error

nchar("hello")

# 5

paste("hello", "world")

# "hello world"

Warm up


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Warm up

Which of these are numbers? What

are the others?How can you tell?

1 "1" "one"

logical

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logical

TRUE or FALSE

R's form of binary data. Useful for logical tests

3 < 4

# TRUE

class(TRUE)

# "logical"

class(T)

# "logical"

factor

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factorR's form of categorical data. Saved as an

integer with a set of labels (e.g. levels).

fac


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Quiz

x


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Aside: dates and times

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s de da es a d es

Surprisingly di$cult for computers!

We won't cover, but I recommend the

following resources

http://www.r-statistics.com/2012/03/do-more-

with-dates-and-times-in-r-with-lubridate-1-1-0/

http://www.jstatsoft.org/v40/i03/

Your turn
http://www.jstatsoft.org/v40/i03/http://www.r-statistics.com/2012/03/do-more-with-dates-and-times-in-r-with-lubridate-1-1-0/


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Your turn

Make a vector that contains the number 1,

the letter R, and the logical TRUE.

What class of data is the vector?

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vec


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Vector

V t 1 2 3


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Vector 1 2 3

Vector 1 2 3


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Vector 1 2 3

numeric

Vector "a" "R" "b"


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Vector a "R" "b"

character

Vector TRUE TRUE TRUE


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Vector TRUE TRUE TRUE

logical

Vector 1 "R" TRUE


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Vector 1 R TRUE

?

Vector "1" "R" "TRUE"


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Vector 1 R TRUE

character

coercion

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logical

numeric

character

coercion

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logical

numeric

character

TRUE

FALSE

1

0

Quiz


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What type of data will result?

c(5, "two")

c(TRUE, "a")

c(1, "TRUE")

TRUE + 5

Quiz


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c(5, "two")

c(TRUE, "a")

c(1, "TRUE")

TRUE + 5

character

Quiz


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c(5, "two")

c(TRUE, "a")

c(1, "TRUE")

TRUE + 5

character

character

Quiz


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What type of data will result?c(5, "two")

c(TRUE, "a")

c(1, "TRUE")

TRUE + 5

character

character

character

Quiz


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c(TRUE, "a")

c(1, "TRUE")

TRUE + 5

character

character

character

Quiz


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c(TRUE, "a")

c(1, "TRUE")

TRUE + 5

character

character

numeric

character

Studio

manual coercion


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as.numeric("1")

as.character(TRUE)

Matrix 1 "R" TRUE


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?

2

3

"S"

"T"

FALSE

TRUE

Matrix "1" "R" "TRUE"


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character

"2"

"3"

"S"

"T"

"FALSE"

"TRUE"



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character

"2"

"3"

"S"

"T"

"FALSE"

"TRUE"

What if you want di"erent datatypes in the same object?

lists and data frames

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listsand data framesgeneralize vectors and

matrices to allow multiple types of data

lists

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A list is a one dimensional group of R

objects.Create lists with list

lst


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List

character



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List

character

1



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List

character

numeric

1



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List

character

numeric

1 "R"



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List

character

characternumeric

1 "R"



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List

character

characternumeric

1 "R" TRUE



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List

character

characternumeric logical

1 "R" TRUE

The elements of a list can be anything. Even

vectors or other lists


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List c(1, 2) c("a", "b", "c")TRUE

list(c(1, 2), TRUE, c("a", "b", "c"))

vectors or other lists.

data frame

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A data frame is a two dimensional group of Robjects.

Each column in a data frame can be a di"erenttype

df


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character

"3" "T" "TRUE"

data frame 1

2

3


"2" "S" "FALSE"


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character

"3" "T" "TRUE"

numeric

data frame 1

2

3


"2" "S" "FALSE"


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character

"3" "T" "TRUE"

numeric

data frame 1 "R"

2

3

"S"

"T"


"2" "S" "FALSE"


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character

"3" "T" "TRUE"

numeric character

data frame 1 "R"

2

3

"S"

"T"


"2" "S" "FALSE"


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character

"3" "T" "TRUE"

numeric character

data frame 1 "R" TRUE

2

3

"S"

"T"

FALSE

TRUE


"2" "S" "FALSE"


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character

"3" "T" "TRUE"

numeric character logical

data frame 1 "R" TRUE

2

3

"S"

"T"

FALSE

TRUE

names

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You can name the elements of a vector, list, or

data frame when you create them.

nvec


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nlst

# $one

# [1] 1

#

# $two

# [1] 2#

# $many

# [1] 3 4 5

ndf


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logic = c(TRUE, FALSE, TRUE

ndf

# numbers letters logic

# 1 1 R TRUE

# 2 2 S FALSE# 3 3 T TRUE

You can also see and set the names with names

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names(ndf)

# [1] "numbers" "letters" "logic"

names(nvec)

# [1] "one" "two" "three"

names(nvec)


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Matrix

Array

Data frame

2D

nD

Studio

helper functions for data structures


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02 the r language part 1

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