问题
I have a database that looks like this:
start<-as.POSIXct("2012-01-15") interval<-60 end<-start+as.difftime(31,units="days") date<-seq(from=start,by=interval*60, to=end) # date/time information l<-length(date) stations<-as.factor(rep(1:3,len=l)) # stations df<-data.frame(date,stations) # data frame
What I would like is to reshape the station column from this data frame into several columns (in this example it will be 3 columns) and calculate the number of time each station was recorded in each date/time row. However, I would like to keep the original date/time column from the data base. If a station was not recorded in one specific date/time, then I want to assign a value of zero.
Ideally, I would like an output like this:
date 1 2 3 2012-01-15 0:00 1 0 0 2012-01-15 1:00 0 1 0 2012-01-15 2:00 0 0 1 2012-01-15 3:00 1 0 0 2012-01-15 4:00 0 1 0 2012-01-15 5:00 0 0 1 2012-01-15 6:00 1 0 0 2012-01-15 7:00 0 1 0 2012-01-15 8:00 0 0 1 2012-01-15 9:00 1 0 0 2012-01-15 10:00 0 1 0
回答1:
You can try to use function dcast() from library reshape2.
library(reshape2)
dcast(df,date~stations,length)
date 1 2 3
1 2012-01-15 00:00:00 1 0 0
2 2012-01-15 01:00:00 0 1 0
3 2012-01-15 02:00:00 0 0 1
4 2012-01-15 03:00:00 1 0 0
回答2:
You could use the function xtabs:
xtabs( ~ date + stations, df)
来源：https://stackoverflow.com/questions/14030283/reshaping-a-column-from-a-data-frame-into-several-columns-using-r