Lecture 1 Flashcards
Intro to R Commands in R Functions in R Navigation hints Variables in R Multiple Values in Variables Using Packages
what’s on the RHS of RStudio (working environment)
output, variables
what’s on the LHS of RStudio
top = instructions to R bottom = console, type commands into R, get output back immediately
does it matter to have space or no space in basic arithmetic in R console? (eg: 10*3 vs 10 * 3)
no
what is the numerical operator commanding ‘power’? (eg: 2 to the power of 3)
numerical operator: ^
eg: 2^3
what is the numerical operator commanding ‘multiplication’? (eg: 2 multiplied by 3)
numerical operator: *
eg: 2*3
what is the numerical operator commanding ‘division’? (eg: 2 divided by 3)
numerical operator: /
eg: 2/3
what is the numerical operator commanding ‘summation’? (eg: 2 summed by 3)
numerical operator: +
eg: 2+3
what is the numerical operator commanding ‘subtraction’? (eg: 2 subtracted by 3)
numerical operator: +
eg: 2+3
what is the logical operator commanding ‘equality’? (eg: 2 + 2 is equal to 4)
logical operator: ==
eg: 2+2 == 4
what is the logical operator commanding ‘inequality’? (eg: 2 + 2 is NOT equal to 5)
logical operator: !=
eg: 2+2 != 5
what is the R’s response to logical operators?
[1] TRUE
or
[1] FALSE
what is the logical operator commanding ‘greater than’? (eg: 4 is greater than 2)
logical operator: >
eg: 4 > 2
what is the logical operator commanding ‘greater than equal to’? (eg: 2 is greater than equal to 2)
logical operator: >=
eg: 2 >= 2
what is the logical operator commanding ‘less than’? (eg: 2 is less than 4)
logical operator: <
eg: 2 < 4
what is the logical operator commanding ‘less than equal to’? (eg: 2 less than equal to 5)
logical operator: <=
eg: 2 <= 5
if T is TRUE, what would R response be when you input ‘T & T’
T & T = if T is TRUE AND T is TRUE, then output would be TRUE
if T is TRUE, what would R response be when you input ‘T | T’
the logical operator ‘|’ means OR
hence T is TRUE OR T is TRUE, then output is TRUE
if T is TRUE, what would R response be when you input ‘T | !T’
the logical operator ‘|’ means OR and the logical operator ! means NOT (!T = False)
hence T is TRUE OR NOT T is TRUE, then output is TRUE
if T is TRUE, what would R response be when you input ‘T & !T’
the logical operator ‘&’ means AND and the logical operator ! means NOT
hence it reads: T is TRUE AND NOT T is TRUE, then output is FALSE
what is T & F, T | F, T & !F, T | !F ???
FALSE, TRUE, TRUE, TRUE
what is F & T, F | T, F & !T, F | !T
FALSE, TRUE, FALSE, FALSE
what is the function sqrt() for
square root
what would Sqrt() show
ERROR because functions in R are case-sensitive. square root function is sqrt() and not Sqrt()
what is the function round()
round up or round down
> round(3.24) ????
[1] 3
what is an argument in function?
function is like a machine, it needs an argument for the machine to operate.
eg: to make orange juice (output) you need juice maker machine (function) and inside the maker u need orange fruits (argument)
a function would always expect one or more argument (eg: pancakes is made of milk, butter, eggs)
> round(3.14159, 4) ???
in this case function round () has more than 1 argument.
the argument means that you wanna round 3.14159 to 4 decimal places
hence,
[1] 3.1416
> round(2, 3.14159) ?????
means that you wanna round 2 to 3.1415 significant figures –> order matters in functions!
hence,
[1] 2
nesting function properties?
it works inside out. hence, the functions inside is worked out first, then after that outside
types of variables?
- numerical: blackbox
what kind of variable is age
numerical variable
if age
- 44
- 64
adding a number to a variable does not change the content of that variable. age is still 34 even thought we added it by 10 in 1
if q
ERROR
requirement for variable names?
- must start with a letter or a period
- letters, numbers, periods c (“0” to “9”) can be used
- underscore (_) can be used, but is best avoided
- name CANNOT contain space or characters like ?,+,!, #, %, (, ), etc
- cannot contain reserved word like TRUE or functions used in R
can you have underscore (_) in your variable name?
yes. underscore can be used, but is best avoided
can variable name contain space?
no. CANNOT contain space
can you put characters like ? in your variable name?
no, name CANNOT contain space or characters like ?,+,!, #, %, (, ), etc
can you put a function name in your variable name?
no. cannot contain reserved word like TRUE or functions used in R
advantages of creating vectors
they can store multiple values
they can be combined into data frames
types of vectors
- numeric (atomic) vector –> number
- character (atomic) vector –> name
- logical (atomic) vector –> TRUE or FALSE
what does “c()” function mean
it is basically saying to put all these values into this particular variable
eg:
> age age
[1] 34 2
age contains the values 34 and 2. 1st element is 34 and 2nd element is 2
what type of vector is involved in this console:
> nerd nerd
[1] TRUE FALSE
logical (atomic) vector.
vector must:
contain the same time to be understandable.
eg: you can’t have numeric and character elements under the same vector at the same time
if:
> person subject mark mark [subject == “RMHI”] ?????
what it means:
marks for people in RMHI
[1] 82 71
if:
> person subject mark subject [mark >= 65 ]
what it means:
subject where people get greater or equal to 65
[1] “RMHI”, “RMHI”, “ARMP”
if:
> person subject mark mark [person == “ann” &+ subject == “RMHI” &+ mark < 50]
what it means:
mark of people who’s name is ANN, takes RMHI, and has mark above 50
response:
numeric (0)
since mark is numeric and there is no element that satisfy those criteria, then numeric (0) is just a vector that contains no elements
what is a package in R?
- collection of user-written collections of functions, data.
- 12000 packages in R
- installed (in your computer)
- loaded (made available for use in R session)
