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Summary Data Science 144 Practical Summaries
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Summaries of all concepts needed in data science 144 practicals, namely RStudios. Practicals 1-5 are covered.
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Notes on tutorial II
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
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