Summary Data Science 144 Practical Summaries

Notes on tutorial I

I
scripts
A text file that holds R code

←
•




extent ion / R
•
:
- r .




projects
Places where you can keep all the files associated with a
project :
input data, scripts ,
results, graphs
>
.
Rproj
> command : Open Project


Lessons from swirl 1)




① Basic building blocks

•

store results in a variable 5+7 →
y
:




data that contains data ) numbers
•
vector : a structure ( object containing a small collection of

> create with the cc ) function

> e. g. C C 1.1
,
9 3.14 )
,

function name

function ?c
•
more info on a
particular : <
no
parenthesis
•
vectors can be used in mathematical expressions
' '
Y
'

arithmetic operators :
' ' '
•
'
+ -
n
, , ,




•

square root :
sqrtc )
•
absolute value : dbsc )

•
with vectors of the same length ,
r
simply performs the arithmetic operation element -




by -

element

if vectors of different lengths the shorter until length
'
is the
'
•
are R recycles vector it same as
,




the longer Vector
; e.
g. 2 * 2 + 100 =
2 * c ( 2,2 , 2) + C C 100
,
100
,
100 )

↓
( 1 2 3)
C , ,




CCI , 2,3 4) C (0 10 )
e.
g. ,
+
,



→ C C 1 2 3, 4) + C CO 10 0 10 )
, , , , ,




object length is not multiple of shorter object length !
"
= I 12 3 14
warning ! longer a

,② workspace and files

R provides a common API ( set of commands ) for interacting with files


•
determine current
working directory :
getwd C)


list all objects local ISC )
in workspace
•
:



•


workspace : what is loaded or created in R 's
memory that can be accessed in this session

variable then Isis throw
"
if you
"
e.
g. assigned 9 to a ×
,
will x


•
list all the files in your working directory using list .fi/esc ) or dirt )
•
use
argsl ) to see what arguments a function can take
"


directory in the working directory dir
"
•
create a current :
.
create c)

• set
your working directory to another directory :
setwdlf.name "




•
create a file in
your working directory : file create 1)
.




check if file file exists C)
•
a exists in the working directory : .




•

access information about the file : file info 1) .




items $ file .info / ) $
" "


grab specific :
operator my test R
project
•



; e.g .
.




•
rename files : file . rename / from
,
to )
•
delete a file : file remove c)
variables
.




see all
make of the file file 1
" "
)
a
copy :
copy Isc )
•




workspace :
.




in
•

provide the relative path to the file : file path .
c)
clear your workspace :
• make a platform-independent pathname : file .


path Cm
,
m )

( list Isu )
directories dir create rm =
•
to create paths / : .




•

to create nested directories ,
'
recursive '
must be set to true
'
( testdir ' '
)
'

> e.
g. dir create ( file . .
path testdirz recursive = TRUE )
, ,




③ Sequences of numbers



•

operator > : creates a sequence of
integers
e.
g.
1 : 4 throws I 23 4


e.
g. pi : 10 creates a
sequence of real numbers :
3,14 . . .



4,14 . . .
5
,
14



4 : I 4 3 2 I
e.
g. >



control
more over a
sequence seqc )
• :




increment by x :

seqcl ,
10
, by = > c)

random of numbers c 5 length 30 )
sequence y seq 10
•
: =
,
,


•
check length of a
sequence :
length c) between sand to

, of length of another sequence :
create a
sequence
◦




> 1 :
length 1)
with
seq c along my sequence )
> =
. _




seq along
( my
seq)
>
_ _




number : 40)
replicate a repcx times
•
=
,



10 )
replicate a vector
rep Coco times
•
:
, 1,23 , =




•


replicate each number a certain amount of times :
repccco 1,23 ,
,
each =D




④ Vectors


atomic vectors : one data type ,
e.
g. numeric
, logical ,
character , integer and complex
lists :
multiple data types


Logical vectors


• values : TRUE , FALSE NA
,




e.
g. num -
Vec < 1 tells us if values are smaller than 1 or not

& !
>
Logical operators !
!
= = = = =
:
, , , , , ,
◦
,
and ,
not




character vectors


•
double
quotes to distinguish character objects
between chars
space
is )
" "

(
" " "


My
"
•
C name
e.
g. , , ↓
"


)
"



join characters of the char vector into single string ( my char collapse
a
paste
◦ =
:
_


,

"

)
"

◦
concatenate :c ( my _
Char ,
m




)
" " "



join char ( world !
"


paste
"
vectors Hello
"
:
Sep
• =

, ,




⑤ Missing values


placeholder for unavailable
> NA : not available ( an
quantity )
•
create a vector
containing 1000 draws from a standard normal distribution : rnorm ( 10007

•
choose a random sample of 100 elements
combining 2 vectors : sample ( cc y 27,100) ,




•
check if elements are NA : is .naC ]

•
TRUE I


•
FALSE 0


i. SUM of TRUE and FALSE gives us the number of TRUES !


> NaN : not a number e.g .
010
,




> Inf :
infinity