Maps and Homebrew.... arghh

I am trying to make a map on which to put the places that the Medical Students have gone on their elective.

I want to use the example of Extradition Treaties as a starting point for at least a map of the world.

I did the easy stuff and copy and pasted the script.

However, it now requires a JSON files entitled: world-50m.json

However, I don't really know how to get this.

This file seems to be a special type of JSON called topojson. I find this a little confusing as surely JSON is JSON but hey....

To use topojson, it seems that I need to install Node.js   - a software platform that provides scalable serve-side applications and networking.

Again why I need to do this is confusing.

Still I have done that.
I opened my terminal window.
I typed brew install node
This created a pile of error messages:

"m095:~ paulbrennan$ brew install node
Warning: Xcode is not installed
Most formulae need Xcode to build.
It can be installed from https://developer.apple.com/downloads/
==> Installing dependencies for node: pkg-config, readline, sqlite, gdbm,
==> Installing node dependency: pkg-config
==> Downloading http://pkgconfig.freedesktop.org/releases/pkg-config-0.28.tar.gz
######################################################################## 100.0%
==> ./configure --prefix=/usr/local/Cellar/pkg-config/0.28 --disable-host-tool -
checking for gcc... clang
checking whether the C compiler works... no
configure: error: in `/private/tmp/pkg-config-5K8f/pkg-config-0.28':
configure: error: C compiler cannot create executables
See `config.log' for more details
Error: Homebrew doesn't know what compiler versions ship with your version
of Xcode (dunno). Please `brew update` and if that doesn't help, file
an issue with the output of `brew --config`:
  https://github.com/Homebrew/homebrew/issues

Note that we only track stable, released versions of Xcode.

Thanks!

READ THIS: https://github.com/Homebrew/homebrew/wiki/troubleshooting

These open issues may also help:
document pkg-config configuration  (https://github.com/Homebrew/homebrew/issues/21129)
m095:~ paulbrennan$"

ADVICE
brew doctor

so I did that....

Again lots of WARNING messages:

Warning: Some directories in /usr/local/share/man aren't writable.
This can happen if you "sudo make install" software that isn't managed
by Homebrew. If a brew tries to add locale information to one of these
directories, then the install will fail during the link step.
You should probably `chown` them:

    /usr/local/share/man/mann

Warning: Xcode is not installed. Most formulae need Xcode to build.
It can be installed from
  https://developer.apple.com/downloads

Warning: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
    /usr/local/lib/libtcl8.6.dylib
    /usr/local/lib/libtk8.6.dylib

Warning: Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected .pc files:
    /usr/local/lib/pkgconfig/tcl.pc
    /usr/local/lib/pkgconfig/tk.pc

Warning: Unbrewed static libraries were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected static libraries:
    /usr/local/lib/libtclstub8.6.a
    /usr/local/lib/libtkstub8.6.a

Warning: You have uncommitted modifications to Homebrew
If this a surprise to you, then you should stash these modifications.
Stashing returns Homebrew to a pristine state but can be undone
should you later need to do so for some reason.
    cd /usr/local/Library && git stash && git clean -d -f

Warning: Your Xcode is configured with an invalid path.
You should change it to the correct path:
  sudo xcode-select -switch /Developer
m095:~ paulbrennan$