update readme to include air quality information

Author: cjber

README.md

@@ -126,7 +126,13 @@ The main domains across our  indicators: retail  services,  health  services, ph
   dataframe of postcodes of which the smallest value for each postcode
   is taken
 
-### 4. Combine into index `ahah/create_index.py`
+### 4. Process air quality data `ahah/process_air.py`
+
+- Create raster of interpolated values from monitoring station points
+  - Exclude points that are _MISSING_
+- Aggregate to LSOA by taking mean values
+
+### 5. Combine into index `ahah/create_index.py`
 
 - Combine both processed secure and open data
 - Intermediate variables calculated

ahah/process_air.py

@@ -1,11 +1,12 @@
 import geopandas as gpd
 import numpy as np
 import pandas as pd
-from ahah.common.logger import logger
-from ahah.common.utils import Config, clean_air, combine_lsoa
 from scipy.interpolate import griddata
 from shapely.geometry import Polygon
 
+from ahah.common.logger import logger
+from ahah.common.utils import Config, clean_air, combine_lsoa
+
 GRID_SIZE = 1000