"R language Combat" reading notes--the fourth chapter basic data management

The contents of this chapter:

Manipulating dates and missing values

Familiarity with conversion of data types

Creation and re-encoding of variables

Sorting, merging and fetching subsets of datasets

Selecting and discarding variables

To say more, data preprocessing time is the longest ... That's true, the amount.

4.1 An example

4.2 Creating a new variable

Arithmetic operators: + 、-、 *,/, ^ (* *) (exponentiation), X-percent Y (take-rest operations), x%/% y (integer division).

Transform function:

The transform function is now available only for data frames. Manipulate the data frame.

Example:

MyData <- transform (mydata,        = x1+x2,        = (x1+x2)/2) #这里的x1和x2是mydata的两列 

For data frame operations, use the transform function more.

"R language Combat" reading notes--the fourth chapter basic data management