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# Remove most objects from the working environment
rm(list = ls())
options(stringsAsFactors = F)
help.start()
# Section 2.2 Data structures
attach(); detach(); with()
# example
summary(mtcars$mpg)
plot(mtcars$mpg, mtcars$disp)
plot(mtcars$mpg, mtcars$wt)
# equal:
attach(mtcars)
summary(mpg)
plot(mpg, disp)
plot(mpg, wt)
detach(mtcars)
# equal:
with(mtcars, {
summary(mpg, disp, wt)
plot(mpg, disp)
plot(mpg, wt)
})
## Section 2.2.6 Lists
# code listing 2.7 Creating a list
g <- "My First List"
h <- c(25, 26, 18, 39)
j <- matrix(1:10, nrow = 5)
k <- c("one", "two", "three")
mylist <- list(title=g, ages=h, j, k)
mylist
str(mylist)
mylist[[2]]
mylist[[1]]
# column
mylist[[3]][,2]
# row
mylist[[3]][2,]
mylist[[4]][1]
# A Note about 'block comments'
if(FALSE) {...}
## Section 2.3.1 Data Input
## Section 2.3.1 Entering Data from keyboard
mydatatxt <- "
age gender weight
25 m 166
30 f 115
18 f 120
"
mydata <- read.table(header = TRUE, text = mydatatxt)
head(mydata)
str(mydata)
class(mydata)
summary(mydata)
write.table(mydata,"mydata.csv", col.names = TRUE,
row.names = TRUE, append = FALSE)
ls() # display current objects
# method 2
mydata <- data.frame(age=numeric(0),
gender=character(0), weight=numeric(0))
mydata <- edit(mydata)
# 2.5. Useful functions for working with data objects
dim(object) # Dimensions of an object.
str(object) # Structure of an object.
class(object) # Class or type of an object.
head(object) # Lists the first part of the object.
tail(object) # Lists the last part of the object.
c(object, object,...) # Combines objects into a vector.
cbind(object, object, ...) # Combines objects as columns.
rbind(object, object, ...) # Combines objects as rows.
rm(object, object, ...) # Deletes one or more objects.
rm(list = Is()) # remove most objects from the working environment.
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