d3Test.js

var postdata;  //used to get the data wanted from d3.xhr() below
function testResults (form) {
  var TestVar1 = form.value1.value;
  var TestVar2 = form.value2.value;
  var TestVar3 = form.value3.value;
  //  var TestVar4 = form.value4.value;
  postdata = "data1=" + TestVar1 + "&data2=" + TestVar2 + "&data3=" + TestVar3;

  // Set the dimensions of the canvas/graph - made it smaller for testing
  var margin = {top: 15, right: 20, bottom: 50, left: 50},
  //width = 900 - margin.left - margin.right,
  //height = 400 - margin.top - margin.bottom;
  width = 300 - margin.left - margin.right,
  height = 135 - margin.top - margin.bottom;

  // Parse the date / time
  var parseDate = d3.time.format("%Y-%m-%d %H:%M:%S").parse;

  // Set the ranges
  var x = d3.time.scale().range([0, width]);
  var y = d3.scale.linear().range([height, 0]);

  // Define the axes
  var xAxis = d3.svg.axis().scale(x).orient("bottom").ticks(5);
  var yAxis = d3.svg.axis().scale(y).orient("left").ticks(5);

  // Define the line
  var valueline = d3.svg.line().x(function(d) { return x(d.tm); }).y(function(d) { return y(d.metric); });
    
  // Adds the svg canvas
  var svg = d3.select("#the_SVG_ID").remove();
  svg = d3.select("body")
    .append("svg")
	.attr("id","the_SVG_ID")  //give the svg a name so we can remove it before updating
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
    .append("g")
    .attr("transform", 
    "translate(" + margin.left + "," + margin.top + ")");

  // Get the data - set header and pass parameters - receive and parse for display
  d3.xhr("testA.php")
    .header("Content-type", "application/x-www-form-urlencoded")
    .post(postdata,function(error, rawData){
    var raw = rawData.responseText.replace(/(^\d+)/,"");
    //alert(raw);  //diagnostic - remove remark to see the clean data returned from database
    var data = JSON.parse(raw);
    data.forEach(function(d) {d.tm = parseDate(d.tm);d.metric = +d.metric;});
	
  // Scale the range of the data
  x.domain(d3.extent(data, function(d) { return d.tm; }));
  y.domain([0, d3.max(data, function(d) { return d.metric; })]);

  // Add the valueline path.
  svg.append("path").attr("class", "line").attr("d", valueline(data));

  // Add the X Axis
  svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis)
    .selectAll("text")  
    .style("text-anchor", "end")
    .attr("dx", "-.75em")
    .attr("dy", ".12em")
    .attr("transform", function(d) {return "rotate(-90)" });

    // Add the Y Axis
    svg.append("g").attr("class", "y axis").call(yAxis);
  });
}