// initialization
window.onload = slideshow;

var currImg = 0;
var charts = [];
// slide show
function slideshow() {
  // find all the charts and put them on the list
    divs = document.getElementsByTagName("div");
    for (var i = 0; i < divs.length; i++) {
      if (divs[i].className == "chart")
	charts.push(divs[i]);
    }
    currImg = 0;
    newSlide();
    // event handler for previous chart
    document.getElementById("prevLink").onclick = function() {
      oldSlide();
        if (currImg == 0)
            currImg = charts.length;
        currImg--;
        newSlide();
    }
    // event handler for next chart
    document.getElementById("nextLink").onclick = function() {
      oldSlide();
        currImg++;
        if (currImg == charts.length)
            currImg = 0;
        newSlide();
    }
}
function oldSlide() {
  charts[currImg].className = "chart";
}
function newSlide() {
  charts[currImg].className = "";
}