NDVI_AVG consists of a set of 12 variables. These variables report the maximum normalized difference vegetation index (NDVI) value within a 10 kilometer circular buffer around each DHS cluster during each calendar month (January through December), averaged over the 2000-2016 timeframe. NDVI is a numeric, normalized index that measures live greenness in an area and can be used as a proxy for vegetation. NDVI values range from 0 to 1.
By adding NDVI_AVG to your data cart, you are in effect adding 12 separate variables (NDVI_JAN - NDVI_DEC), one variable for each month.
Please see the User Note on Using IPUMS-DHS Contextual Variables: NDVI [URL omitted from DDI.] for the data source, methodology, and more detailed information about these variables.
Environmental Variables -- PERSON
Imputation and derivation
NDVI_AVG variables are numeric variables between 0 and 1.