Revise installation instructions in README

Updated installation instructions for R and celestial package, including troubleshooting steps.

Author: asgr

README.md

@@ -10,38 +10,6 @@ Core package containing a collection of common astronomical conversion routines
 
 ## Installation
 
-### Getting R
-
-First things first, you will probably want to install a recent version of **R** that lets you build packages from source. The advantage of choosing this route is you can then update bleeding edge versions directly from GitHub. If you rely on the pre-built binaries on CRAN you might be waiting much longer.
-
-#### Mac
-
-For Mac just get the latest binaries from the **R** project pages:
-
-<https://cloud.r-project.org/bin/macosx/>
-
-#### Windows
-
-For Windows just get the latest binaries from the **R** project pages:
-
-<https://cloud.r-project.org/bin/windows/>
-
-#### Linux
-
-Debian:	`sudo apt-get install r-base r-base-dev`
-
-Fedora:	`sudo yum install R`
-
-Suse:	More of a pain, see here <https://cloud.r-project.org/bin/linux/suse/README.html>
-
-Ubuntu:	`sudo apt-get install r-base-dev`
-
-All the info on binaries is here: <https://cloud.r-project.org/bin/linux/>
-
-Now you have **R** installed (hopefully) I would also suggest you get yourself **R-Studio**. It is a very popular and well maintained **R** IDE that gives you a lot of helpful shortcuts to scripting and analysing with **R**. The latest version can be grabbed from <https://www.rstudio.com/products/rstudio/> where you almost certainly want the free Desktop version.
-
-### Getting celestial
-
 Source installation from GitHub should be easy:
 
 ```R
@@ -50,31 +18,6 @@ remotes::install_github("asgr/celestial")
 library(celestial)
 ```
 
-A few Mac people seem to have issues with the above due to the backend used to download files. A work around seems to be to either use devtools:
-
-```R
-install.packages('devtools')
-devtools::install_github("asgr/celestial")
-library(celestial)
-```
-
-Or try the following:
-
-```R
-Sys.setenv(R_REMOTES_NO_ERRORS_FROM_WARNINGS="true")
-remotes::install_github("asgr/celestial")
-```
-
-If all of these do not work then the nuclear option is to download (or clone) the GitHub repo, cd to where the tar.gz file is and run in the **console** (or **Terminal** on Mac):
-
-```console
-R CMD install celestial_X.Y.Z.tar.gz
-```
-
-where X, Y and Z should be set as appropriate for the version downloaded (check the name of the file basically).
-
-Failing all of the above, please raise an Issue here.
-
 #### Package Dependencies
 
 The above should also install the required packages. If you have trouble with this you can try installing the required packages manually first and then retry the installation for **celestial**:
@@ -121,7 +64,7 @@ deg2dms(-27.345, type='cat', sep='dms')
 Compute cosmological distances and related quantities for a given redshift:
 
 ```R
-cosdist(z=1, H0=70, OmegaM=0.3)
+cosdist(z=1:10, H0=70, OmegaM=0.3)
 ```
 
 This returns a data.frame with columns including comoving distance, luminosity distance, angular diameter distance, look-back time, and more.
@@ -156,7 +99,7 @@ coordref = cbind(RA=c(10.1, 10.5, 11.0), Dec=c(-20.1, -20.5, -21.0))
 coordcompare = cbind(RA=c(10.11, 10.6, 12.0), Dec=c(-20.09, -20.4, -22.0))
 
 # Match within 10 arcsec
-match = coordmatch(coordref, coordcompare, rad=10)
+match = coordmatch(coordref, coordcompare, rad=10, radunit = 'amin')
 ```
 
 ### WCS Projections