colorLookup to assign colors to nominal data

[jbfaden]

Since Autoplot renders events as a solid bar and there's typically no room for labels, it would be nice if the server could suggest that colors be used depending on the data. With my HAPI prototyping server, I have the weather conditions as indicated by the NOAA website where I collect the data. It has condition labels like "Fair" and "Mostly Cloudy", which are coded "CLR" and "SCT085". I convey these in the stream https://jfaden.net/HapiServerDemo/hapi/info?id=icwc in 12 bytes.

To color these, I add to the info node:

    "x_colorLookup": {
                "(?i).*cloud.*": "LightSteelBlue",
                "(?i).*rain.*": "LightGreen",
                "(?i).*storm.*": "DarkGreen",
                "(?i)overcast": "LightGrey",
                "Fair": "SkyBlue"
            },
     "x_colorLookup_about": "http://jfaden.net/HapiServerDemo/moreabout/extensions.html#colorLookup"

The lookup table is a list of regular expressions and then the web color name to use. See https://www.w3schools.com/colors/colors_names.asp for web color names. See https://regexr.com/ which is a tool for creating regular expressions. (It also shows that different languages use different syntax for regular expressions, for example its equivalent is /overcast/i .) Note the x_colorLookup_about doesn't point to anything, which is a bug.

[jbfaden]

Note Jon's MMS group at UNH requested that Autoplot color data based on data values, for example to mark points as red because a sensor has reported data outside nominal values. In this case instead of regular expressions and nominal data, we could have something like:

    "x_colorLookup": {
           ".gt(50)": "Red",
           ".gt(40).and(le(50))": "Yellow",
           ".le(40)": "Green"
    }

But it might be better to have nominal labels for these as well (ERROR,WARNING,info).

[jbfaden]

Another use case for this would be to display the data in a spreadsheet, where the cell background color is picked using the lookup.