tm_crs consistency with the book

[Nowosad]

In the https://tmap.geocompx.org/map-projections#sec-map-projection-properties section, we explain four properties -- Conformal, Equal area, Equidistant, and Azimuthal. However, the `tm_crs():

1. Uses the preservation property as the values for the property argument. Have you considered allowing to specify, e.g., distance and equidistant?
2. It does not offer the azimuthal property. Have you considered adding it?

Also, should we update the order of columns in this table to be consistent with the order in the tm_crs() function?

[Nowosad]

@mtennekes

[mtennekes]

Good questions. The book table is taken from some (theoretical) sources. The implementation is done thanks to suggestions from @mdsumner

Now I have:

		# impute family
		proj = switch(crs_extra,
			area = "laea",
			distance = "aeqd",
			shape = "stere",
			"laea"
		)

Is there a proj family we can use for azimuthal?

[Nowosad]

"aeqd" should be good for directions also...

proj <- switch(crs_extra,
  area       = "laea",
  distance   = "aeqd",
  shape      = "stere",
  direction  = "aeqd",
  conformal  = "stere",
  equalarea  = "laea",
  equidistant= "aeqd",
  azimuthal  = "laea",
  "laea"
)