R Language--tapply,sapply (actions of factors and lists)

Recently participated in a small game where the tapply,sapply (lapply) function can quickly achieve my purpose and effectively reduce the amount of code

F	Description
Tapply (X,F,G)	X is a vector, F is a factor column, G is an action function, and a similar operation with a data frame can be done by using the by function
Sapply (LIST,G)	G is the operation function, the return result is a vector, and the lapply return result is the list form. Often used in combination with split

Example

Data for 980 bus different stations of the number of passengers on the statistics

Line Name	License plate number	Arrival Site	Number of boarding	Start Boarding Time	end of boarding time
980	Yue BM8475	14	11	2014-06-09 07:08	2014-06-09 07:13
980	Yue BM8475	13	3	2014-06-09 07:14	2014-06-09 07:15
980	Yue BM8475	12	10	2014-06-09 07:17	2014-06-09 07:17
980	Yue BM8475	10	5	2014-06-09 07:20	2014-06-09 07:20
980	Yue BM8475	8	1	2014-06-09 07:22	2014-06-09 07:22

Count the number of passengers at different stations

(Freq <-tapply (data[,4], data[,3], sum))
  1   2   3   4   5   6   7   8  9 
257 325 164 174 186 205  80 118 267 259 130  

According to the license plate number classification, separately counts the number of different stations

Data <-split (data, data$ license plate number)   # #对数据按照车牌号分组
Freq <-sapply (data, function (data) {
  tapply (data$ Number of passengers, data$ arrival site, sum)
})  # #按照车牌号统计不同站点上车人数
freq[1] # #查看结果
$ yue BM8475
 1   2   3   4   5   7   8   9  ten  6  15   2   4   7   3   1

Summary

The proficiency of the two data types, the factor, the list, will have a deeper understanding of the power of R.