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I calculated mean from a raster for a single polygon using zonal statistics as table tool and got the mean as 440,000.

The raster is the exact same shape as the polygon (used extract by mask tool for this). When I open the attribute table of this raster and do field statistics on the value field, I see that the mean is 330,000.

Shouldn't the two means be the same if not exactly the same?

  • To calculate mean for raster a)see properties B) total of count*value/ total of count. Field statistic gives you nothing – FelixIP Nov 24 '16 at 17:28
  • Your comment made me think clearly and you are right field statistic on the value field gives nothing because it doesnt take into account the counts. Thanks! – Salman Nov 24 '16 at 19:11
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I just realised that its wrong to do a field statistic for mean on this value field because this value field in the raster attribute table does not show the values of all the cells in that raster. It shows only all the unique values with the cell count being shown in the 'count field'. So cannot expect to calculate mean from here by just doing field statistics. Using the zonal statistics tool is the right way.

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