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Rbasics-1.R
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Rbasics-1.R
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# Rbasics-1.R
# Feb 2023
# this is a comment!!!
# this is the editor window for writing R script
# 1. Basic Math
1 + 1
4/2
4/3
sqrt(2)
# 2. Variables
x <- 3 # see result in the environment window
x
4 -> y # not recommended
y
z = 5 # also not recommended
z
rm(z) # remove var
z
# 3. Data Types
# 4 main types:
# (1) Numeric
# (2) Character (String)
# (3) Date
# (4) Logical (TRUE/FALSE)
# 3.1 Numeric
x <- 4
class(x)
is.numeric(x)
is.integer(x)
y <- 4L # integer
class(y)
is.numeric(y)
is.integer(y)
# integer is a subset of numeric (used less frequently)
# promote type when needed
class(2.8)
class(4L)
class(4L * 2.8)
# 3.2 Character (String)
y <- "Hello"
y
class(y)
z <- factor("Hello")
z
class(z) # explained further in vectors
nchar(y)
nchar(z) # Error
nchar(1234)
# 3.3 Dates
date1 <- as.Date("2021-11-12")
date1
class(date1)
as.numeric(date1) # number of days since 1 Jan 1970
date2 <- as.POSIXct("2021-11-12 9:00")
date2
class(date2)
as.numeric(date2) # number of secs since 1 Jan 1970
# 3.4 Logical
x <- TRUE
x
class(x)
is.logical(x)
TRUE * 5
FALSE * 5
y <- !x
y
T
F
x <- T
x
# *Note: T could be a var name
T <- 7
x <- T
x
class(x)
rm(T)
T
TRUE <- 7 # TRUE can't be a var name
# so use full TRUE/FALSE always
2==3
2<=3
"chiangmai" == "chiangrai"
"chiangmai" < "chiangrai"
# 4. Vectors
x <- c(1,2,3,4,5,6,7,8,9,10)
x
class(x)
# 4.1 Vector operations
x * 3
x + 3
x / 4
x ^ 2
sqrt(x)
1:10
10:1
-2:3
5:-7
x <- 1:10
y <- -5:4
x + y
x / y
length(x)
length(y)
length(x+y)
x
x + c(1,10)
x + c(1,2,3) # warning
x <= 5
(x <- 10:1)
(y <- -4:5)
any(x<y)
all(x<y)
q <- c("Banana","Mango","Apple","Orange")
nchar(q)
y
nchar(y)
x
x[1] # index start from 1
x[1:2]
x[c(1,4)]
y <- rep(c(-1,0,2),3)
y
z <- seq(0,1,length.out = 9)
z
class(z)
is.integer(z)
is.numeric(z)
# 4.2 Factor vector / categorical data
q1 <- c("Banana","Mango","Apple","Orange","Mango","Apple","Mango","Apple","Banana","Mango")
q1
class(q1)
q2 <- factor(q1)
q2 # alphabetical order
class(q2)
as.numeric(q2)
# Ordinal
q3 <- factor(c("M.Eng", "M.Eng", "B.Eng","M.Eng", "D.Eng", "B.Eng"), levels = c("B.Eng","M.Eng","D.Eng"))
q3
as.numeric(q3)
# 5. Calling Functions
x <- 1:6
x
mean(x)
?mean
# 6. Missing Data
# 6.1 NA
z <- c(1,2,NA,4,NA,6)
z
mean(z)
mean(z, na.rm = TRUE)
is.na(z)
# 6.2 NULL
z <- c(1,2,NULL,4,NULL,6)
z
#################################################################################