here xyz gis --ratio / --calculate

[burritojustice]

Simple version:

Let users calculate and save a ratio as a new property in a feature, based on two existing properties.

here xyz gis --ratio property1,property2

Many scenarios where this would be useful, e.g. people per square km, or $/sq.m,

We could let the user name the property:

here xyz gis --ratio cost,area,'$ per sq.ft`

or call it something like xyz_ratio@property1÷property2 if they don't add a name.

More complicated version:

I was initially thinking about this as an extension of gis --area, but this brings up the possibility of allowing simple, general purpose field calculations with operators… something like:

here xyz --gis calculate new_property=property1/property2

here xyz --gis calculate new_property=property1+property2

here xyz --gis calculate new_property=property1*property2

etc.

• we could also have an interactive feature that lets you pick properties and operators.

• for more complex calculations, we could allow JavaScript Math Object operators

• or we could even allow a constrained js function with conditional statements (which is one of the common use cases of something like the expressions in the QGIS field calculator

• there is some interesting overlap with conditional operations and Rule Based Tags