R/plot_ts.R

In USGS-R/trainR: Example package for learning how to develop R packages.

#' Timeseries plotting function
#' 
#' Plot a timeseries by giving the x and y data.
#' 
#' @param xdat dates for the x axis
#' @param ydat data for the y axis
#' @param y.axis.label name to put on the y axis, defaults to "Y Value"
#' @param color chr, color of plotted symbol
#' @return plot of timeseries
#' @importFrom graphics axis plot
#' @examples 
#' color <- "blue"
#' plot_ts(as.Date("2010-08-15"),10,color=color)
#' @export
plot_ts <- function(xdat, ydat, y.axis.label="Y Value", color="red"){
  if(class(xdat)!="Date") { 
    stop("xdat must be a Date") 
  }
  
  plot(xdat, ydat, xlab = "Date", ylab = y.axis.label, pch=20, 
       col=color, las=1, tck=0.02, axes=FALSE, frame.plot = TRUE)
  
  
  # If dates span > 1 year, change axis label format
  data.years <- as.numeric(format(xdat, "%Y"))
  data.years.uniq <- unique(data.years)
  if(length(data.years.uniq) > 1){
    axis(side = 1, las=1, tck=0.02,
         at = pretty(xdat), labels = format(pretty(xdat), "%D"))
  } else {
    axis(side=1)
  }
  
  axis(side=2, las=1, tck=0.02)
  axis(side=3, las=1, tck=0.02)
  axis(side=4, las=1, tck=0.02)
}