var WIDTH = 800;
var HEIGHT = 600;

var runs = [
    {
        id: 1,
        date: 'October 1, 2017',
        distance: 5.2
    },
    {
        id: 2,
        date: 'October 2, 2017',
        distance: 6.4
    },
    {
        id: 3,
        date: 'October 3, 2017',
        distance: 8.7
    }
]

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

var yScale = d3.scaleLinear();
yScale.range([HEIGHT, 0]);
yDomain = d3.extent(runs, function(datum, index){
    return datum.distance;
})
yScale.domain(yDomain);

d3.select('svg').selectAll('circle')
    .data(runs)
    .enter()
    .append('circle');

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

var parseTime = d3.timeParse("%B%e, %Y");
var xScale = d3.scaleTime();
xScale.range([0,WIDTH]);
xDomain = d3.extent(runs, function(datum, index){
    return parseTime(datum.date);
});
xScale.domain(xDomain);

d3.selectAll('circle')
    .attr('cx', function(datum, index){
        return xScale(parseTime(datum.date));
    });