Many thanks to [Tim's answer](http://stats.stackexchange.com/a/178164/92827), as this pointed me in the right direction to look for a scatter plot.

I started going down the route of learning R or using Python's matplotlib, but I think I'm going to settle on just using Highcharts with plain old HTML and javascript. I was hoping my end result would be on an internal website anyway, so this is probably closer to what I need.

Here's a screenshot of a demo I came up by modifying Highchart's [Scatter plot demo](http://www.highcharts.com/demo/scatter):

[![Scatter Plot Demo][1]][1]

The code for that is:


    <script src="//code.jquery.com/jquery-1.11.3.min.js"></script>
    <script src="http://code.highcharts.com/highcharts.js"></script>
    <script src="http://code.highcharts.com/modules/exporting.js"></script>
    
    <div id="container" style="min-width: 310px; height: 400px; max-width: 800px; margin: 0 auto"></div>
    
    <script type="text/javascript">
    $(function () {
        $('#container').highcharts({
            chart: {
                type: 'scatter',
                zoomType: 'xy'
            },
            title: {
                text: 'Email Queue Throughput by Agent Per Weekday'
            },
            subtitle: {
                text: 'Help Scout Cases 9/22 - 9/26'
            },
            xAxis: {
                title: {
                    enabled: true,
                    text: 'Day of Week'
                },
                startOnTick: true,
                endOnTick: false,
                showLastLabel: true,
                allowDecimals: false,
                categories: ['Sunday','Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']
            },
            yAxis: {
                title: {
                    text: 'Hour of day'
                }
            },
            legend: {
                layout: 'vertical',
                align: 'left',
                verticalAlign: 'top',
                floating: false,
                backgroundColor: (Highcharts.theme && Highcharts.theme.legendBackgroundColor) || '#FFFFFF',
                borderWidth: 1
            },
            plotOptions: {
                scatter: {
                    marker: {
                        radius: 5,
                        states: {
                            hover: {
                                enabled: true,
                                lineColor: 'rgb(100,100,100)'
                            }
                        },
                        symbol: "circle"
                    },
                    states: {
                        hover: {
                            marker: {
                                enabled: false
                            }
                        }
                    },
                    tooltip: {
                        headerFormat: '<b>{series.name}</b><br>',
                        pointFormat: 'hour: {point.y}'
                    }
                }
            },
            series: [{
                name: 'Ben',
                color: 'rgba(223, 83, 83, .5)',
                data: [[1,1], [1,2], [1,3],
                       [2,1.5], [2,2.7], [2,3.8],
                       [3,4], [3,3.5], [3,3.6],
                       [4,2], [4,5], [4,7],
                       [5,1], [5,2], [5,5]]
    
            }, {
                name: 'Ashley',
                color: 'rgba(119, 152, 191, .5)',
                data: [[1.1,1],   [1.1,2],   [1.1,3],
                       [2.1,1.5], [2.1,2.7], [2.1,3.8],
                       [3.1,4],   [3.1,3.5], [3.1,3.6],
                       [4.1,2],   [4.1,5],   [4.1,7],
                       [5.1,1],   [5.1,2],   [5.1,5]]
            }]
        });
    });


  [1]: https://i.sstatic.net/dBC1t.png