Set Y-axis grid density in Rickshaw.js

Question

I have a graph detailing wind speeds where I would like to have the grid on the Y axis have ticks every 5 (m/s). How do I set the density of the Y axis grid?

// triggered when data has been loaded via ajax
$graph.on('graph.render', function(e, d) {
    var graph, y_axis;

    // Fixtures
    palette = new Rickshaw.Color.Palette();

    graph = new Rickshaw.Graph( {
        element: $graph.find('.chart');
        width: $graph.innerWidth() - 20,
        height: $graph.innerHeight() - 20,
        series: [
            {
                key: 'min',
                name: 'Min Wind Speed',
                color: palette.color(),
                data: d[0].data
            } // ...
        ]
    });

    x_axis = new Rickshaw.Graph.Axis.Time({
        graph: graph,
        timeUnit: {
            seconds: 600,
            formatter: function(d) {
                return d.toUTCString().match(/(\d+:\d+):/)[1];
            }
        }
    });

    y_axis = new Rickshaw.Graph.Axis.Y( {
        graph: graph,
        orientation: 'left',
        element: $graph.find('.y-axis')
    });
});

Answer 1

You could set the number of ticks via ticks or the values to display via tickValues explicitly:

var yAxis = new Rickshaw.Graph.Axis.Y( {
  graph: graph,
  tickFormat: Rickshaw.Fixtures.Number.formatKMBT,
  //ticks: 5, //static number of ticks, only works 
  tickValues: [50,100,150,200,250,300,350], // values to use/display
  element: document.getElementById('y_axis')
} );

You would use either ticks or tickValues, not both. If you use tickValues as above and your max y value is 180, the y-scale would only show the values [50,100,150,200], 250 and above would not be shown. If you add more data with a higher y-value, the scale would automatically re-scale and show the higher values as specified by you.

More information about ticks and tickValues can be found at the D3's SVG axes page.