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Building python script to compute weekly average from daily rainfall rasters

Question asked by tlupher on Apr 19, 2012
Latest reply on Sep 17, 2014 by lpalao
Using:  ArcGIS 10 SP4 (ArcInfo) student evaluation with all extensions.

Goal: I need help finding a solution to integrate the cell statistics tool using Python to create a new weekly rainfall average layer for each week of 490 consecutive days of raster data.

Data: I have 490 raster files(.tif) of rainfall amounts for each day. Each raster was converted from a corresponding shapefile containing i) an even-spaced grid of points with no coincident points and ii) the same amount of grid points.

Example Raster for one day of data:

So far this is my logic for how to do this using Python:

0) Import arcpy, env from arcpy
1) Set workspace directory containing raster data for 490 consecutive days
2) Create list of rasters in workspace (rasterList = arcpy.ListRasters("*", "tif"))
3) Checkout spatial analyst extension

While rasterList is not empty
4) Create 7 variables for the first 7 consecutive days of rasters
5) Call Cell_Statistics function:  outCellStatistics = CellStatistics([raster1,..., raster7], "MEAN", "NODATA")   
6) Save new output raster:"C:/sapyexamples/output/week1")
7) Populate next consecutive 7 days into variables raster1,...,raster7
8) Repeat steps 5 to 7 for 70 iterations (70 weeks)

I have tried messing around with the example in ArcGIS 10.0 Desktop Help. I am having an explicit problem with assigning the next 7 raster files into the 7 input variables for the next iteration. Any advice is appreciated.