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) Monthn 15 31 26 30 37 31 48 31 59 30
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