R/scale_x_yearmonth.R

In galacticpolymath/galacticEdTools: Tools for inspiring K-16 students to become interdisciplinary experts and agents of change for a better tomorrow

#' scale_x_yearmonth
#'
#' Makes y-axis have year as a bottom facet, with abbreviated months as minor axis-labels.
#'
#' Code inspired by \href{http://www.jasonfabris.com/blog/dteformat/}{This post by Jason Fabris}
#'
#' @param abbrev How long to make months? Default=1 means just first letter of month; NA is full month name.
#' @param breaks.mnth Frequency of month labels; default= 1 (every month)
#' @param mnth.size Font size of month labels; default=12 (pts)
#' @param yr.size Font size of year labels; default=16 (pts)
#' @param yr.var Variable name for year; default= "Year"
#' @param ... other arguments for \code{\link[ggplot2]{scale_x_date}}
#' @examples

#' require(ggplot2)
#' #Set up time series dataset
#' df<-data.frame(date=as.Date(c(sapply(1949:1952,function(yr) {paste(yr,1:12,1,sep="-")}))),
#' passengers=as.vector(AirPassengers)[1:48])
#' df$year<-sprintf("%.4s",df$date)
#' (g <- ggplot(df,aes(date,passengers))+geom_point())
#' #Now break show months and year on x-axis
#' #(doesn't work, because it expects a year variable called "Year")
#' \dontrun{
#' (g2 <- g+scale_x_yearmonth())
#' }
#' #Try that again
#' (g2 <- g+scale_x_yearmonth(yr.var="year"))
#' #Now let's use GP styling for legibility from a distance.
#' #(Note themes have to come before the scaling layer).
#' (g3 <- g2+theme_galactic(base.theme="gray")+scale_x_yearmonth(yr.var="year"))
#' #This is a bit packed; let's only show every 3 months
#' g3+scale_x_yearmonth(abbrev=3,breaks.mnth=3,yr.var="year")
#' #Note that if you want to show a trend line, you can't currently do this across years,
#' #because we're really faceting for each year to trick ggplot into making 2 types of axis label
#' g3+scale_x_yearmonth(abbrev=3,breaks.mnth=4,yr.var="year")+geom_smooth()
#' @export

scale_x_yearmonth=function(abbrev=1,breaks.mnth=1,mnth.size=12,yr.var="Year",yr.size=16,...){
  dte_formatter <- function(x) {
    #formatter for axis labels:
    mth <- substr(format(x, "%b"),1,abbrev)
    mth
  }
list(ggplot2::scale_x_date(date_breaks=paste0(breaks.mnth," months"),labels=dte_formatter,...),
    ggplot2::theme(strip.background=ggplot2::element_blank(),strip.placement="outside",panel.spacing.x=unit(0,"lines"),
                   panel.border=ggplot2::element_rect(colour="#363636",fill="transparent",size=.35),
                   strip.text=ggplot2::element_text(colour = "#363636",size=yr.size),
                   axis.text.x=ggplot2::element_text(size=mnth.size)),
    ggplot2::facet_wrap(eval(parse(text=paste0("~",yr.var,collapse=""))), nrow = 1, scales = "free_x", shrink = FALSE, strip.position = "bottom"),
    {}
     )

}