i having trouble getting values instead of factors output of mapply function. code below tries find temperature @ particular location , time.
now <- sys.time() datetime<-as.posixct(seq(now, length.out = 5, = "hours"), tz = "gmt") location<-c("chicago","detroit","new york","cleveland","atlanta") temperature<-c(2,9,4,8,59) df1 <- data.frame(datetime, location, temperature) # add 3 hours system time <- sys.time() + 3*60*60 datetime<-as.posixct(seq(now, length.out = 5, = "hours"), tz = "gmt") location<-c("chicago","cleveland","chicago","detroit","atlanta") temperature<-c(6,8,3,12,69) df2 <- data.frame(datetime, location, temperature) # data frame location , time , temperature data loc_temp_df <- rbind(df1,df2) # add 2 hours system time <- sys.time() + 2*60*60 datetime<-as.posixct(seq(now, length.out = 7, = "hours"), tz = "gmt") location<-c("chicago","chicago","new york","atlanta","new york", "detroit", "cleveland") df <- data.frame(datetime, location) # function find temperature @ specific location closest specific time myfunction <- function(x,y) { same_location <- loc_temp_df[which(loc_temp_df$location == y),] time_at_location <- as.posixct(same_location$datetime, format = '%y-%m-%d %h:%m:%s', tz = "gmt") index <- which.min(abs(difftime(x, time_at_location, "mins"))) same_location[index,] } mapply(myfunction, df$datetime, df$location) when run code factors returned instead of values. idea how can return values instead of factors?
[,1] [,2] [,3] [,4] [,5] [,6] [,7] datetime 1436564283 1436564283 1436560683 1436567883 1436560683 1436575083 1436567883 location factor,1 factor,1 factor,1 factor,1 factor,1 factor,1 factor,1 temperature 6 6 4 59 4 12 8 i tried using lapply not work in same way.
you can use either map or simplify=false in mapply keep list , rbind.
do.call(rbind,map(myfunction, df$datetime, df$location)) or
do.call(rbind, mapply(myfunction, df$datetime, df$location, simplify=false)) 
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