为data.frame中的每个唯一ID编写多个excel文件

Question

I want to write an Excel file for each unique ID with required date range. The below is a snapshot of raw data in text.

ID,Type,PostCode,Date
15,SS,2520,2015-11-01
15,SS,2520,2015-10-01
20,SS,2520,2015-11-20
16,SS,2520,2015-11-12
16,SS,2520,2015-10-25
11,SS,2520,2015-10-14
20,SS,2520,2015-11-30

The data can have 100+ of individual ID with more than 100 thousand rows. I want to read the raw data and write the separate excel file with the data table in required date range for each ID ideally with the file name of ID number.

My attempt

myfunction <- function(startdate, enddate) {
x <- read.table("aaa.text", sep = ",")
split(x,x$ID)
}

Any advice or suggestion would be very much appreciated.

Answer 1

Using data.table and xlsx , the following will do the trick:

library(data.table)
library(xlsx)
setDT(x)
x[ , write.xlsx(.SD, file = paste0(.BY[[1]], ".xlsx")), by = Date]

From there, it's bells and whistles.

You'll notice this prints a column of row names -- write.xlsx has an option to turn this off ( row.names = FALSE ).

If you want to include Date as a column in your output, it'll be a tiny bit more nebulous (props to Frank for cleaning it up):

x[ , write.xlsx(c(.BY, .SD), file = paste0(.BY[[1]], ".xlsx")), by = Date]

Basically, because .SD and .BY are both list s, c just concatenates, and apparently write.xlsx works fine on lists.