Work Directory (WD), History, Source, Comm
WD - is the computer folder with the file you read in or save out.
getwd()
See current WD
getwd()
Set, change WD
dir()
Lists content of the dir
History
savehistory(file="Name.Rhistory")
loadhistory(file="Name.Rhistory")
sink("name.txt")
sink()
open-close connection
Source
source("CommandScript.R")
Commands stored in scripts in WD
Created objects saved and loaded in the WD:
save(object, file="path")
load(file="path")
Commands
Erase all objects in the workspace and list rest:
rm()
ls()
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Data types
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Atomic (fundamental) Data Types? complex:
raw:
numeric:
character:
logical:
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Hierarchy? Character > Double > Integer > Logical
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Loading Data
read.table
(file="name.txt")
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txt data frame |
read.csv2
(file="name.csv")
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csv data frame |
read.spss
(file="name.spss")
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spss data frame |
data
(name, package="pkg")
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builtin dataset |
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opens a spreadsheet |
read.file
(file="name.spss")
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Iibrary psych
import functions. |
Parsing
A parser converts the textual representation of R code into an internal form which may then be passed to the R evaluator.
(p1<-parse(text="3*(2+4)"))
expression(3*(2+4))
eval(p1)
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Abstract Syntax Trees (AST) that are parsed according to the language grammar |
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Vectors
Vectors two types:
Atomic: all elements same type
List: a generalized vector, elements can have different types |
Ex: vec <- c(1, 5, 4, 9, 0)
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Name the elements: (vec <- c(Frodo=1, Bilbo=5, Gandalf=4))
length(x)
3 |
Access the 1st element; remove the 3rd element vec[1]; vec[-3]
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Access the last element using the length vec[length(vec)]
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Access more elements vec[c(1,3)]
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Remove more elements vec[-c(1,3)]
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Access only elements that are greater than 3 vec[vec>3]
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Replace one or more elements vec[c(1,3)]<-c(1,3)
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Access only elements that are not NA vec[!is.na(vec)]
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Repeating rep(2,5) = c(2,2,2,2,2)
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Sequencing seq(2,5,1)
2,3,4,5 |
Matrices are long Vectors matrix(1:4,2) + c(1,2)
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R performs operations on vectors element by element |
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