X-Axis Customization: Practical JavaScript Solutions for Better Date Handling
When creating visualizations in Knowi, handling date and time fields on the x-axis can sometimes present challenges. The default behavior for displaying the x-axis is driven by a logic that may not always match your specific needs, leading to misaligned or missing dates on your charts. In this blog, I'll share some practical JavaScript scripts you can use to customize the x-axis in your Knowi visualizations. Whether you're looking to adjust tick intervals, display specific dates, or control how your time-based data is shown, these examples will help you fine-tune your charts for a more accurate and visually appealing presentation. The following scripts can be placed in the widget footnote of any X/Y axis type widgets.
Script 1:
Sometimes, Knowi charts will only display a midpoint tick, leaving the start and end intervals open. This can make the chart look incomplete, especially when visualizing data over a specific range. This script forces the chart to display the start and end tick marks, ensuring that all intervals are clearly represented.
<script>
var widget = document.currentScript.closest('.widget');
var widgetBody = widget.querySelector('.body');
var chartIndex = widgetBody.dataset.highchartsChart;
var chart = Highcharts.charts[chartIndex];
if (chart) {
chart.xAxis[0].update({
startOnTick: true,
endOnTick: true
});
}
</script>
Use Case: This is particularly helpful when you’re comparing data across a defined time period, such as weekly or monthly sales figures, and want to ensure both the start and end of the period are clearly marked.
Script 2:
By default, the intervals on the x-axis may not always match your desired units. This script allows you to manually define the units, such as forcing the chart to display data by days. One thing to keep in mind: in smaller windows, this customization may result in overlapping labels if the space is too tight.
<script>
var widget = document.currentScript.closest('.widget');
var widgetBody = widget.querySelector('.body');
var chartIndex = widgetBody.dataset.highchartsChart;
var chart = Highcharts.charts[chartIndex];
if (chart) {
chart.xAxis[0].update({
units: [
['day', [1]]
]
});
}
</script>
Use Case: This script is useful when you need to ensure a consistent display of time intervals, like showing daily data points in a time series. Just be cautious with chart sizing to avoid label overlap.
Script 3:
For even greater precision, this script allows you to set custom tick intervals using milliseconds. In this example, we’re setting the interval to one day (calculated in milliseconds) so that each tick represents a full 24-hour period.
<script>
var widget = document.currentScript.closest('.widget');
var widgetBody = widget.querySelector('.body');
var chartIndex = widgetBody.dataset.highchartsChart;
var chart = Highcharts.charts[chartIndex];
if (chart) {
chart.xAxis[0].update({
tickInterval: 1000 * 60 * 60 * 24
});
}
</script>
Use Case: This is ideal when you're working with precise time intervals, such as hourly or daily data in a high-frequency dataset, and need to manually control the spacing of each tick.
Script 4:
If your dataset includes specific dates and you want to plot one tick per date, this script ensures each date is represented. One limitation is that the space between ticks will be evenly distributed, which may not accurately reflect gaps in the data. To address this, you can use a date injection function to fill in the missing dates.
<script>
var widget = document.currentScript.closest('.widget');
var widgetBody = widget.querySelector('.body');
var chartIndex = widgetBody.dataset.highchartsChart;
var chart = Highcharts.charts[chartIndex];
if (chart) {
var tickPositions = [];
chart.xAxis[0].series.forEach(function(s){
s.data.forEach(function(d){
if (d.y !== 0 && tickPositions.indexOf(d.x) === -1)
tickPositions.push(d.x)
});
});
chart.xAxis[0].update({
tickPositions: tickPositions
});
}
</script>
Use Case: This script is useful when you want each specific date in your dataset to appear as a tick, such as when plotting sporadic events or project milestones. If your data has gaps, consider using a date injection function to fill in those missing points for more accurate spacing.
Customizing the x-axis in Knowi charts can greatly improve the clarity and accuracy of your visualizations. By using these scripts, you can ensure your date and time data is presented exactly as you need it, whether you’re controlling tick intervals, defining specific units, or ensuring all relevant dates are displayed.
Take the time to experiment with these scripts and see how they can enhance the way your data is visualized. Knowi's flexibility, combined with the power of JavaScript, allows for deep customization that will elevate the quality of your charts.
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