Docs updates, data downloader

README.md

@@ -12,6 +12,14 @@ Clone this repository:
 ```bash
 git clone https://github.com/bmorris3/mrspoc.git
 ```
+Run this command to download a local copy of the required TGAS data, Hipparcos, 
+and  interferometric radius tables:
+```
+cd mrspoc
+python download_data.py
+```
+You can delete the data archive `data.tar.gz`.
+
 Create an environment variable that contains the path to the `data/` directory, 
 called `MRSPOC_DATA_DIR`. For example, add the following line to your `~/.cshrc`:
 ```

download_data.py

@@ -0,0 +1,23 @@
+"""
+Download and extract the data archive from the web.
+"""
+
+import tarfile
+import os
+from urllib.request import urlretrieve
+
+data_archive_path = 'data.tar.gz'
+data_archive_url = 'http://staff.washington.edu/bmmorris/docs/data.tar.gz'
+p = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'data')
+
+# Write local copy of the data archive:
+print('Downloading (150 MB) and extracting data to "{0}"...'.format(p))
+urlretrieve(data_archive_url, data_archive_path)
+
+# Extract all files from the gzipped tar archive
+with tarfile.open(data_archive_path, 'r|gz') as f:
+    f.extractall()
+
+# Remind the user to set an environment variable:
+print('Now set an environment variable "MRSPOC_DATA_DIR" to the path to the '
+      'data, directory {0}'.format(p))