Fixed scale of X axis and never change amcharts

Question

If you can see on X axis There are increment of time 6 hour Now, I want to change its scale to 2 hour

I just learn this amchart yesterday and really don't know so much on how to use it.

here is the code

<script type="text/javascript">
//am4core.useTheme(am4themes_kelly);

am4core.useTheme(am4themes_animated);
// Themes end


// Create chart
var chart = am4core.create("chartdiv", am4charts.XYChart);
chart.paddingRight = 20;

chart.data = generateChartData();

var dateAxis = chart.xAxes.push(new am4charts.DateAxis());
dateAxis.baseInterval = {
  "timeUnit": "minute",
  "count": 1
};
dateAxis.tooltipDateFormat = "HH:mm, d MMMM";

var valueAxis = chart.yAxes.push(new am4charts.ValueAxis());
valueAxis.tooltip.disabled = true;
valueAxis.title.text = "Fin 1";

var series = chart.series.push(new am4charts.LineSeries());
series.dataFields.dateX = "date";
series.dataFields.valueY = "visits";
series.tooltipText = "Stacker: [bold]{valueY}[/]";
series.fillOpacity = 0.3;

chart.cursor = new am4charts.XYCursor();
chart.cursor.lineY.opacity = 0;
chart.scrollbarX = new am4charts.XYChartScrollbar();
chart.scrollbarX.series.push(series);


chart.events.on("datavalidated", function () {
    dateAxis.zoom({start:0, end:1});
});


function generateChartData() {
    var chartData = [];
    // current date
    var firstDate = new Date();
    // now set 12:00 am
    firstDate.setHours(0,0,0,0);

    // and generate 500 data items
    var visits = 0;
    for (var i = 0; i < 1442; i++) {
        var newDate = new Date(firstDate);
        // each time we add one minute
        newDate.setMinutes(newDate.getMinutes() + i);

        chartData.push({
        date: newDate,
        visits: visits
        });

    }
    return chartData;
}
</script>

I have edit the code and available to edit here: https://codepen.io/muhammad-syazani/pen/wLrbQE

Answer 1

Yeah working with the Date Axis can be tricky. Even if you've been working with amCharts v4 for a while, it may not be clear how to tame the axis the way you want. I highly recommend reading our guide on the Date Axis in full, that will really help. The chart will basically try and figure out how it can fit a frequency nicely into the chart.

The first thing you want to adjust is the dateAxis.renderer.minGridDistance. By default, its 120 pixels. The sample chart has 24 hours, with a minimum pixel interval of 120px for every 2 hours, your chart.plotContainer area would have to be 120 * (24/2), or at least 1440px, your browser window would have to be even wider than that. So if we cut that down, we're more likely to be able to fit a 2-hour interval grid.

The next thing, and this is the main ingredient, is the dateAxis.gridIntervals. If you check out the generated documentation, you'll see a list of intervals the chart will choose from. There's hourly, or every 3 hours, but not every 2 hours. If we replace that list with one that has a 2-hour interval, if it can fit, the chart will use that.

You'll want to do the same on the scrollBarX's date axis as well.

Relevant code:

dateAxis.renderer.minGridDistance = 75; // 75 * 24/2 == 900 minimum plotContainer width requisite

var gridIntervals = [
 { timeUnit: "millisecond", count: 1 },
 { timeUnit: "millisecond", count: 5 },
 { timeUnit: "millisecond", count: 10 },
 { timeUnit: "millisecond", count: 50 },
 { timeUnit: "millisecond", count: 100 },
 { timeUnit: "millisecond", count: 500 },
 { timeUnit: "second", count: 1 },
 { timeUnit: "second", count: 5 },
 { timeUnit: "second", count: 10 },
 { timeUnit: "second", count: 30 },
 { timeUnit: "minute", count: 1 },
 { timeUnit: "minute", count: 5 },
 { timeUnit: "minute", count: 10 },
 { timeUnit: "minute", count: 30 },
 { timeUnit: "hour", count: 1 },
 { timeUnit: "hour", count: 2 }, // This is the 2-hour interval
 { timeUnit: "hour", count: 3 },
 { timeUnit: "hour", count: 6 },
 { timeUnit: "hour", count: 12 },
 { timeUnit: "day", count: 1 },
 { timeUnit: "day", count: 2 },
 { timeUnit: "day", count: 3 },
 { timeUnit: "day", count: 4 },
 { timeUnit: "day", count: 5 },
 { timeUnit: "week", count: 1 },
 { timeUnit: "month", count: 1 },
 { timeUnit: "month", count: 2 },
 { timeUnit: "month", count: 3 },
 { timeUnit: "month", count: 6 },
 { timeUnit: "year", count: 1 },
 { timeUnit: "year", count: 2 },
 { timeUnit: "year", count: 5 },
 { timeUnit: "year", count: 10 },
 { timeUnit: "year", count: 50 },
 { timeUnit: "year", count: 100 }
];
dateAxis.gridIntervals.setAll(gridIntervals);

chart.scrollbarX.events.on("validated", function() {
  chart.scrollbarX.scrollbarChart.xAxes.getIndex(0).gridIntervals.setAll(gridIntervals);
});

Fork:

https://codepen.io/team/amcharts/pen/9ba62a5bb5239fee149c2d46bf1e4b81

Hope this helps!

(Btw - Salaams! I like the username, is that a Fairy Tail reference?)