1 예제

2 sqldf 에러

3 참고자료

install.packages("sqldf")
library("sqldf")
x <- head(warpbreaks)
sqldf("select * from warpbreaks limit 5")
sqldf("select * from warpbreaks where breaks >= 50")
sqldf("select wool, sum(breaks) from warpbreaks group by wool")

> sqldf("select * from warpbreaks limit 5")
Loading required package: tcltk
  breaks wool tension
1     26    A       L
2     30    A       L
3     54    A       L
4     25    A       L
5     70    A       L
> sqldf("select * from warpbreaks where breaks >= 50")
  breaks wool tension
1     54    A       L
2     70    A       L
3     52    A       L
4     51    A       L
5     67    A       L
> sqldf("select wool, sum(breaks) from warpbreaks group by wool")
  wool sum(breaks)
1    A         838
2    B         682

install.packages("sqldf")
library("sqldf")
cname <- c("x1", "x2", "x3","x4", "x5", "x6", "y")
german = read.table("c:\\data\\german1.txt", col.names = cname)
head(german)
sqldf("select x1, sum(x2) sum_x2, count(distinct x4) distinct_x4 from german group by x1")

#사용자 정의함수 사용?
DF <- data.frame(a_date = 0:1, c = 0:1)

processDates <- function(data, ...) {
ix <- grepl("_date$", names(data))
names(data)[ix] <- sub("_date$", "", names(data)[ix])
data[ix] <- lapply(data[ix], as.Date, origin = "1970-01-01")
data
}

sqldf("select * from DF", method = processDates)


#파라미터 처리
p1 <- 7
fn$sqldf("select * from iris where Sepal_Length > $p1")

#Update
DF <- data.frame(a = 1:3, b = c(3, NA, 5))
sqldf(c("update DF set b = a where b is null", "select * from main.DF"))

DF <- data.frame(a = 1:3, b = factor(c(3, NA, 5))); DF
sqldf(c("update DF set b = a where b is null", "select * from main.DF"), method = "raw")

#PostgreSQL이 설치되고, 서비스가 시작되어 있어야 함.
#https://code.google.com/p/sqldf/#12._How_does_one_use_sqldf_with_PostgreSQL?
library("RPostgreSQL")

> sqldf("select * from d order by cid");
Error in .local(drv, ...) : 
  Failed to connect to database: Error: Can't connect to MySQL server on 'localhost' (0)
Error in !dbPreExists : invalid argument type

sqldf("select * from d order by cid", drv="SQLite");

• https://code.google.com/p/sqldf/
  
• http://cran.r-project.org/web/packages/sqldf/sqldf.pdf