var WIDTH = 800;
var HEIGHT = 600;

var runs = [
    {
        id: 1,
        date: 'October 1, 2017 at 4:00PM',
        distance: 5.2
    },
    {
        id: 2,
        date: 'October 2, 2017 at 5:00PM',
        distance: 7.0725
    },
    {
        id: 3,
        date: 'October 3, 2017 at 6:00PM',
        distance: 8.7
    }
];


d3.select('svg')
    .style('width', WIDTH)
    .style('height', HEIGHT);

var yScale = d3.scaleLinear(); //create the scale
yScale.range([HEIGHT, 0]); //set the visual range (e.g. 600 to 0)
yScale.domain([0, 10]); //set the data domain (e.g. 0 to 10)

d3.selectAll('circle').data(runs)
    .attr('cy', function(datum, index){
        return yScale(datum.distance);
    });

var xScale = d3.scaleTime(); //scaleTime maps date values with numeric visual points
xScale.range([0,WIDTH]);
xScale.domain([new Date('2017-10-1'), new Date('2017-10-31')]);

var parseTime = d3.timeParse("%B%e, %Y at %-I:%M%p"); //this format matches our data in the runs array
var formatTime = d3.timeFormat("%B%e, %Y at %-I:%M%p"); //this format matches our data in the runs array
d3.selectAll('circle')
    .attr('cx', function(datum, index){
        return xScale(parseTime(datum.date)); //use parseTime to convert the date string property on the datum object to a Date object, which xScale then converts to a visual value
    });