Basic data management for R

1. Creating new variable for existing data frame

mydata<-data.frame(x1 = c(2, 2, 6, 4), x2 = c(3, 4, 2, 8))

1.mydata$sumx <- mydata$x1 + mydata$x2

mydata$meanx <- (mydata$x1 + mydata$x2)/2

2.attach(mydata) mydata$sumx <- x1 + x2

mydata$meanx <- (x1 + x2)/2

detach(mydata)

3.mydata <- transform(mydata, sumx = x1 + x2, meanx = (x1 + x2)/2)

2.Recoding Variables

e.g. recode the age into categorical variable agecat(Young, Middle aged, Elder)

 

change variable name 

1. fix()

2. 

 Missing Value

 

 

 

 Sorting data

order() 

the sorting order is normally ascending.

Merging datasets