Node-red-dashboard Chart rewrite epoch time X axis labels

[johnwalicki]

Dave CJ - There are several Weather Company APIs that return historical data that I would like to plot in charts. I build the chart data series with Epoch time as the X axis. It looks fine but the X axis labels are somewhat meaningless. I was wondering if there is a way to set the labels to a date format. Something like 06-23-2020 06-24-2020 06-25-2020
-- John

Two examples:

[Colin]

The timestamps should be in javascript milliseconds.
I looks like they are wrong. Show us some of the data that you are sending to the chart and tell us what the timestamps represent.

[johnwalicki]

The timestamps are in seconds 1593342000 (one timestamp per day)
The chart is correct but the x-axis autoselects meaningless tick marks.
Here's a function that builds a chart of 30 days of temperature data (the data is looking backwards in time so I reverse it for the chart)

var MonthlyHistoryTempChart = [{
    "series":["Daily Temp Max", "Daily Temp Min"],
    "data":[[],[]],
    "labels":["Daily Max Temp", "Daily Min Temp"]
}];

for( var i=(msg.payload.validTimeUtc.length)-1; i >= 0 ; i--) {
    MonthlyHistoryTempChart[0].data[0].push( {"x":msg.payload.validTimeUtc[i],"y":msg.payload.temperatureMax[i] } ) ;
    MonthlyHistoryTempChart[0].data[1].push( {"x":msg.payload.validTimeUtc[i],"y":msg.payload.temperatureMin[i] } ) ;
}

msg.payload = MonthlyHistoryTempChart;
return msg;

[johnwalicki]

Essentially, I want to set the underlying chart.js options to label the x-axis as days.

From the chart.js docs I see:
https://www.chartjs.org/docs/latest/axes/cartesian/time.html#time-units
which tells me to set the options object. How can I pass this through the node-red-dashboard chart node to the underlying chart.js?

var chart = new Chart(ctx, {
    type: 'line',
    data: data,
    options: {
        scales: {
            xAxes: [{
                type: 'time',
                time: {
                    unit: 'day'
                }
            }]
        }
    }
});

[johnwalicki]

Searching through this forum, I see some chart.js examples which use the ui_template node. I was hopeful that I wouldn't need to go down that path for a common time series use case.

[johnwalicki]

gah - I'm going to crawl under my rock again. Dave is brilliant and has already provided this capability. Not certain when it became an option in the Chart node.