如何根据R中列的行值的子字符串选择data.table?
我们经常在R中创建数据子集,以根据数据分析项目中整个目标的较小目标进行计算。有时,此子集以字符串而不是数值为条件。我们还可以data.table使用grep函数基于列的行值的子字符串创建一个子集。
示例
考虑以下data.table对象-
x1<-c("Lucknow","Kanpur","Chennai","Delhi","Mumbai","Jammu","Jodhpur","Jaipur","Ludhiana","Dehradun","Aligarh","Bareilly","Cuttack","Sonipat","Gurgaon","Noida","Bengluru","Kolkata","Ahmedabad","Patna") S.No<-1:20 IndianCities<-data.table(x1,S.No) IndianCities输出结果
x1 S.No 1: Lucknow 1 2: Kanpur 2 3: Chennai 3 4: Delhi 4 5: Mumbai 5 6: Jammu 6 7: Jodhpur 7 8: Jaipur 8 9: Ludhiana 9 10: Dehradun 10 11: Aligarh 11 12: Bareilly 12 13: Cuttack 13 14: Sonipat 14 15: Gurgaon 15 16: Noida 16 17: Bengluru 17 18: Kolkata 18 19: Ahmedabad 19 20: Patna 20
子集可以按如下所示完成-
示例
IndianCities[grep("il",x1)] x1 S.No 1: Bareilly 12 IndianCities[grep("ac",x1)] x1 S.No 1: Cuttack 13 IndianCities[grep("a",x1)]输出结果
x1 S.No 1: Kanpur 2 2: Chennai 3 3: Mumbai 5 4: Jammu 6 5: Jaipur 8 6: Ludhiana 9 7: Dehradun 10 8: Aligarh 11 9: Bareilly 12 10: Cuttack 13 11: Sonipat 14 12: Gurgaon 15 13: Noida 16 14: Kolkata 18 15: Ahmedabad 19 16: Patna 20 IndianCities[grep("b",x1)] x1 S.No 1: Mumbai 5 2: Ahmedabad 19 IndianCities[grep("c",x1)] x1 S.No 1: Lucknow 1 2: Cuttack 13 IndianCities[grep("g",x1)] x1 S.No 1: Aligarh 11 2: Gurgaon 15 3: Bengluru 17 IndianCities[grep("at",x1)] x1 S.No 1: Sonipat 14 2: Kolkata 18 3: Patna 20 IndianCities[grep("o",x1)] x1 S.No 1: Lucknow 1 2: Jodhpur 7 3: Sonipat 14 4: Gurgaon 15 5: Noida 16 6: Kolkata 18 IndianCities[grep("u",x1)] x1 S.No 1: Lucknow 1 2: Kanpur 2 3: Mumbai 5 4: Jammu 6 5: Jodhpur 7 6: Jaipur 8 7: Ludhiana 9 8: Dehradun 10 9: Cuttack 13 10: Gurgaon 15 11: Bengluru 17