Cumulative sum through a list of rasters

CamiSunley

Hi everyone, 

I have a list of rasters named: "ih1", "ih2", "ih3", ..., "ih28" that represent the interpolated rainfall height in the corresponding time step (hour). I want to calculate the cumulative rainfall height in each time step which is the sum of the rainfall in the same step and the cumulative rain of the previous one, e.g. CumRain(i) = ih(i) + CumRain(i-1). I am trying to code this in arcpy yet the "i" thing does not work for rasters.

If you have any idea how this could be solved, let me know.

Thanks a lot !

DanPatterson

Convert the raster s to numpy arrays

RasterToNumPyArray—ArcGIS Pro | Documentation

 

a0 
array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

a1
array([[16, 17, 18, 19],
       [20, 21, 22, 23],
       [24, 25, 26, 27],
       [28, 29, 30, 31]])

a2 
array([[32, 33, 34, 35],
       [36, 37, 38, 39],
       [40, 41, 42, 43],
       [44, 45, 46, 47]])

np.cumsum((a0, a1, a2), axis=0)

array([[[ 0,  1,  2,  3],
        [ 4,  5,  6,  7],
        [ 8,  9, 10, 11],
        [12, 13, 14, 15]],

       [[16, 18, 20, 22],
        [24, 26, 28, 30],
        [32, 34, 36, 38],
        [40, 42, 44, 46]],

       [[48, 51, 54, 57],
        [60, 63, 66, 69],
        [72, 75, 78, 81],
        [84, 87, 90, 93]]], dtype=int32)
​# ---- or  np.nancumsum(a, axis=0) if you have nodata cells

 

Now if you want an intermediate time step, just slice it

 

csum = np.nancumsum(a, axis=0)
csum[1]
array([[16, 18, 20, 22],
       [24, 26, 28, 30],
       [32, 34, 36, 38],
       [40, 42, 44, 46]], dtype=int32)

 

Then if you need raster s back

NumPyArrayToRaster—ArcGIS Pro | Documentation