R 컬럼 셀렉트
install.packages(‘sqldf’)
install.packages(‘data.table’)
install.packages(‘ggplot2’)
install.packages(‘KoNLP’)
library(sqldf)
library(data.table)
emp<-read.csv
emp<-read.csv(“c:/image/emp.csv”,header=TRUE)
sqldf(“SELECT ename,sal,hiredate FROM emp”)
컬럼 가져오기: emp$ename
중복 제거하고 컬럼 가져오기: data.table(unique(emp$job))
표로 정리하기: 테이블명[열,행] emp[,c(“ename”,”sal”)]
emp[emp$hiredate==’1981-09-08′,c(“ename”,”hiredate”)]
emp[emp$sal<=1000&emp$sal>=300,c(“ename”,”sal”)]
emp[emp$job!=’MANAGER’,c(“ename”,”job”,”sal”)]
ename job
1 홍길동2 MANAGER
3 ALLEN SALESMAN
4 WARD SALESMAN
5 JONES MANAGER
6 MARTIN SALESMAN
7 BLAKE MANAGER
8 CLARK MANAGER
11 TURNER SALESMAN
emp[emp$job %in% c(“MANAGER”,”SALESMAN”),c(“ename”,”job”)]
emp[!emp$job %in% c(“MANAGER”,”SALESMAN”),c(“ename”,”job”)]
ename sal
3 ALLEN 1600
12 ADAMS 1100
A로 시작하는
emp[grep(“^A.*”,emp$ename),c(“ename”,”sal”)]
ename sal
3 ALLEN 1600
12 ADAMS 1100
T로 끝나는 모든 사람
emp[grep(“*.T$”,emp$ename),c(“ename”,”sal”)]
ename sal
9 SCOTT 3000
널값 가져오기
emp[is.na(emp$comm),c(“ename”,”comm”)]
ename comm
2 SMITH NA
8 CLARK NA
10 KING NA
12 ADAMS NA
13 JAMES NA
14 FORD NA
낫널 가져오기
emp[!is.na(emp$comm),c(“ename”,”comm”)]