R - dplyr 包

新增列 Mutate

Mutate is used to add new variables to the data. For example lets adds a new column that displays the temperature in Celsius.

mutate(airquality, TempInC = (Temp - 32) * 5 / 9)

抽样 Sample

The sample function is used to select random rows from a table. The first line of code randomly selects ten rows from the dataset, and the second line of code randomly selects 15 rows (10% of the original 153 rows) from the dataset.

获取指定条数样本：

sample_n(airquality, size = 10)

获取指定比例样本：

sample_frac(airquality, size = 0.1)

统计 Count

The count function tallies observations based on a group. It is slightly similar to the table function in the base package. For example:

count(airquality, Month)

  Month  n

1     5 31

2     6 30

3     7 31

4     8 31

5     9 30