Relative date on x-axis

[Romainpetit]

Problem
I'm using plotly to display timed data, but here the exact date is of no importance, only the relative time between the values is. I'm wondering if there is any existing setting about this.

For the moment, I get this result with tickmode: 'auto', type: 'date'

Wish
I'd like to set my first point as the zero, and then have all other times relative to it.
The tick would display the time relatively to this first date :

Since I'll be displaying various data of different time scales, tickformat is of little help. I'd need an automatic date formatter with customizable format settings.

This is related to this debate on the pertinence of this automatic date format: #99

Any help appreciated!

[etpinard]

That's an interesting proposition. I've never came across a special relative time format in other graphing library. @Romainpetit Does that exist anywhere else?

In your case (in JS at least), it would be pretty easy to convert your x coordinates to milliseconds (i.e with new Date().getTime()) from that base time step and pass that to Plotly.plot.

[Romainpetit]

I don't know a graphing library that offers such a relative time in its options @etpinard.
This specific point is manageable tough: I can process my data in milliseconds by substracting the first point's timestamp to all points values, like you said.

Now with this relative timing in ms,

• In plotly, I can display it telling xaxis to use type: 'linear': that will display it as a quantity unit. I can have the s unit display with ticksuffix: "s" and try to have some formatting for large number with tickformat. But still, we're only showing seconds.
• In an environment where I have more control, I can use a JS time formatting library like moment.js or dateformat.js to render this time in ms to time-formatted data: ms, s, h, day ...

Other option seems to be to dig in the formatTime(), ms2DateTimeLocal() or formatTime() functions in plotly's dates.js file, to get a well-formatted time output that fits my needs.

[etpinard]

In plotly, I can display it telling xaxis to use type: 'linear': that will display it as a quantity unit. I can have the s unit display with ticksuffix: "s" and try to have some formatting for large number with tickformat. But still, we're only showing seconds.

You can also try tickvals / ticktext to customize your axis labels (see example https://codepen.io/etpinard/pen/YWEdJX?editors=0010). This solution might not behave as desired on zoom, but it should get you close to what you want.

[etpinard]

This ticket won't directly result in a PR, so I'll close it.

Thanks for writing in @Romainpetit