#cran.r

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Misc. & Shortcuts

abs(x)**absolute value of x

sqrt(x)**principal sqrt of x

x can be any numeric or complex vector display

for complex vectors

abs(x)==Mod(x) and sqrt(x)==x^0.5

$

! 

indicative of ‘logical negation, or not’

for example: x<-rnorm(x),y<-rnorm(y), is.na(x)//should return all false, when perform y<-x[!is.na(x)], will recall a list of new y values (identical to x) because 

!indicates or as in present all index values that are not true

since there are no NA values, should display all x values

&, &&

signifies ‘logical AND 

|,||

signifies OR

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Objects: Intrinsic Attributes

Every object in this environment has 2 intrinsic qualities or properties

(1) mode(x) ---  Mode- “basic type of its fundamental constituents”; for example

there can be ‘empty’ objects that have a mode, to assign mode: e<-numeric() --- e[3]<-17-- e-- NA, NA, 17

(2)length(x) --- Length- for a simple vector: will list the number of values (n) contained in the numeric/character string///for a matrix/dataframe: it will list the # of dimensions (for ex: piracy has one row, rate, one column

       to change length// length(objectname)<- new numerical length

attributes(x) --- details the non-intrinsic properties associated with the object, to select/assign specific attribute use function attr(object,name) 

class(x) -- details the class (all obj in r have) of object, for simple vectors (numer, character, list, matrix) for data frames it is more complex

Mode- Revisited

as.something(x)------as.character/integer

this program operates modal change using this function

have you ever wanted your #s to appear in quotations? or your words to appear as integers?(warning, word characters to numbers does not work-- will return NA values)

z<-c(1:4) g<-as.character(z)---’1′ ‘2′ ‘3′ ‘4′

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Vectors: Index, and Modification

character quantities (or values) and character strings are used

vector of character strings

Discussed in next section

paste() function

you can take an arbitrary # of arguments and merges them into 1 set of character strings, specify the sequence range, and the mode of separation (quotations, tabs)

example: paste(c(’X’,’Y’),1:10 or 1:20, sep=‘’) will produce: c("X1", "Y2", "X3", "Y4", "X5", "Y6", "X7", "Y8", "X9", "Y10")

logical vector 

remember the is.na() function? this can create a vector, using the length of the var, omitting the FALSE values and selecting variables that are TRUE

positive vector integral qualities

x<-rnorm(x), x[1]==1, x[[2]]==1.1, x[1:10]

[] indicates integer/index focused operations

so positive VIQs (vector integral qualities) will indicate a recall the corresponding index value 

negative vector integral qualities

use this when you want to display all data except the range you provide

g<-x[-(1:100)] will display all x index values, except for those between the first and ninth indexes

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Missing Values in a Vector

NA 

indicates that not all values of a vector are known, any operation involving NA will give the output NA

is.na(variablename) 

will produce a logical vector, if TRUE appears, then a value is NA, if all FALSE, no values=NA

NaN- are not a number values, not the same as NA

this happens when you divide 0 by 0 or subtract infinity-infinity

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Logic, Sequence, Repetition

using colons, number:number or seq()

the colon sequence command has high operative function, so if you do 2*20:40 R will compute 2*20, 2*21, 2*22, etc.

seq(-1,1)= -1,0,1 is the same as -1:1 same as seq(from=-1, to=1,by=1)

from=, to=, by= (increment)

rep(variable, times=, each=)

logical vectors

you can set variables to be true given certain conditions, for ex (overtime<-x>8)

if c1 and c2 are logical vectors (like the one above), then 

for exact equality use <,>,<=,>=,== OR

  != for inequality or !c1 is the negation of c1

c1&c2 for their intersection and

c1|c2 for their union or

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Simple Data Structures

data structures

named arrays by which R operates

vector

a single entity consisting of ordered collection of numbers (numeric vectors are simplest data structures)

vectorname<-c(value1,value2);

you can assign a vector in any order, the <-/->  is a shortcut for the ‘assign’ statement using function c( )

function c( ) can take up an arbitrary # of vector arguments

assign(’vectorname’,c(value1,value2))

matrix

“a matrix is just a data array with 2 subscripts”

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Output Files

sink

In order to set out an output file with your existing commands enter the function

sink.number()

reports how many files are running in environment

source(’commands.R’)

you can load recorded commands (pre-existing external files) using this

sink(’newfile.lis’)

this will send “subsequent outputs to external file newfile.lis

sink()

will restore outputs to environment again

Naturally with this program, all objs created are stored permanently in afile for use in future sessions (objects written .RData and command lines are saved to .RHistory

recommended to use diff working directories for objs in this enviro, don’t want overlapping vectors