hours = function(timestamps){ # converts timestamps into hour of the day.
  days = timestamps %>% unlist %>% as.POSIXlt(origin = "1970-01-01") %>%
    as.character %>%
    map(function(x){if(is.na(x)){return(c("NA","NA"))}else{return(strsplit(x, " "))}}) %>%
    unlist %>%
    matrix(nrow=2) %>%
    t
    days = days[,1]
  
    hours = as.POSIXlt(timestamps, origin = "1970-01-01") #%>% 
    hours <- unclass(hours)
    reformat <- matrix(NA, nrow = length(hours[[1]]), ncol = length(hours))
    for (i in 1:11) {
     reformat[,i] <- hours[[i]]
    }
    reformat <- apply(reformat, 2, as.numeric) #NA introduced by coercion
    reformat <- data.frame(reformat)
    #add variable names 
    colnames(reformat) <- c("sec", "min", "hour","mday", "mon", "year","wday", "yday", "isdst", "zone", "gmtoff")
  
    hours <- reformat %>%
    dplyr::select(hour, min, sec) %>%
    apply(1, function(times) sum(times * c(1, 1/60, 1/3600) ) )
  output = as_data_frame(cbind(hours=hours, days=days))
  output["hours"] = lapply(output["hours"], as.numeric)
  return(output)
}