scale_y_duration displays time in sec, min, hour or day depending on max value

scale_y_duration

library(ggplot2)
scale_y_duration <- function(..., units = c("s","min","h","day")){
  units <- match.arg(units, c("ms","seconds","minutes","hours","days", "weeks", "months", "years"),
                     several.ok = TRUE)
  # to get them in the right order
  units <- intersect(c("ms","seconds","minutes","hours","days", "weeks", "months", "years"), units)

  ms    <- 1/1000
  min   <- 60
  h     <- 60 *min
  day   <- 24 *h
  week  <- 7 * day
  year  <- 365.25 * day
  month <- year / 12
  
  labels <- function(x){
    max_x <- max(x, na.rm=TRUE)
    
    if("years" == units[[1]] || max_x > 3 * year && "years" %in% units){
      # > 3 year, use years
      x <- x /year
      x <- paste(round(x,2),"years")
    } else if("months" == units[[1]] || max_x > 3 * month && "months" %in% units){
      # > 3 months, use months
      x <- x /month
      x <- paste(round(x,2),"months")
    } else if("weeks" == units[[1]] || max_x > 3 * week && "weeks" %in% units){
      # > 3 weeks, use weeks
      x <- x /week
      x <- paste(round(x,2),"weeks")
    } else if("days" == units[[1]] || max_x > 3 * day && "days" %in% units){
      # > 3 days, use days
      x <- x /day
      x <- paste(round(x,2),"days")
    } else if("hours" == units[[1]] || max_x > 3 * h && "hours" %in% units){
      # > 3 h, use h
      x <- x /h
      x <- paste(round(x,2),"h")
    } else if("minutes" == units[[1]] || max_x > 3 * min && "minutes" %in% units){
      # > 3 min, use min
      x <- x /min
      x <- paste(round(x,2),"min")
    } else if("seconds" == units[[1]] || max_x > 3 * min && "seconds" %in% units){
      # > 3 min, use min
      x <- paste(round(x,2),"s")
    } else if("ms" %in% units){
      # > 3 min, use min
      x <- x /min
      x <- paste(round(x,2),"min")
    } else {
      stop("no unit was found for provided value of x")
    }
  }
  
  breaks <- function(x){
    max_x <- max(x, na.rm=TRUE)
    if("years" == units[[1]] || max_x > 3 * year && "years" %in% units){
      # > 3 year, use years
      scales:::extended_breaks()(x/year) * year
    } else if("months" == units[[1]] || max_x > 3 * month && "months" %in% units){
      # > 3 months, use months
      scales:::extended_breaks()(x/month) * month
    } else if("weeks" == units[[1]] || max_x > 3 * week && "weeks" %in% units){
      # > 3 weeks, use weeks
      scales:::extended_breaks()(x/week) * week
    } else if("days" == units[[1]] || max_x > 3 * day && "days" %in% units){
      # > 3 days, use days
      scales:::extended_breaks()(x/day) * day
    } else if("hours" == units[[1]] || max_x > 3 * h && "hours" %in% units){
      # > 3 h, use h
      scales:::extended_breaks()(x/h) * h
    } else if("minutes" == units[[1]] || max_x > 3 * min && "minutes" %in% units){
      # > 3 min, use min
      scales:::extended_breaks()(x/min) * min
    }  else if("seconds" == units[[1]] || max_x > 3 && "seconds" %in% units){
      # > 3 s, use s
      scales:::extended_breaks()(x)
    } else if("ms" %in% units){
      scales:::extended_breaks()(x/ms) * ms
    } else {
      stop("no unit was found for provided value of x")
    }
  }
  scale_y_continuous(..., labels = labels, breaks = breaks)
}

df <- data.frame(x=1:3, time = c(1,2,5))
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration() + ggtitle("seconds")

df <- data.frame(x=1:3, time = c(1,2,5) * 1000)
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration() + ggtitle("min")

df <- data.frame(x=1:3, time = c(1,2,5) * 10000)
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration() + ggtitle("hours")

df <- data.frame(x=1:3, time = c(1,2,5) * 100000)
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration() + ggtitle("days")

df <- data.frame(x=1:3, time = c(1,2,5) * 1000)
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration(units = "h") + ggtitle("force hours")

df <- data.frame(x=1:3, time = c(1,2,5) * 1000000)
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration() + ggtitle("not weeks, by default")
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration(units = c("day","week","month")) + ggtitle("weeks")
                                                                                                                      
df <- data.frame(x=1:3, time = c(1,2,5) * 10000000)
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration(units = c("day","week","month")) + ggtitle("months")
ggplot(df, aes(x, time)) + geom_point() + scale_y_duration(units = c("year")) + ggtitle("force year")

more flexible now, we can choose a set of units.
Even more flexible would be to set the thresholds through the unit parameter, now it's always 3, meaning, if "hours" is part of units (as is by default) and max(ime) is more than 3 hours, we'll use hours.
A flexible argument would allow something lile units = list("s","min", h = 10)