topic Re: Aggregate raster doesn't have "Mode" function in ArcGIS Spatial Analyst Questions

Aggregate raster doesn't have "Mode" function

AndrewOrr — Mon, 07 Feb 2011 16:57:46 GMT

Hello,
I am trying to take a set of 30m cells representing slope values as integer values and aggregate them to various larger-sized cells (in separate files of course). To do this, for my data I would like to have the aggregated cell values be derived by the "Mode" of the original input cells. The options for the aggregate tool include Min., Max, Median, Mean, and Sum., but there is no Mode option.

Does anyone have a procedure for deriving an aggregate with the Mode of input cells?

Thanks much for your help,
-Andy

Re: Aggregate raster doesn't have "Mode" function

curtvprice — Mon, 07 Feb 2011 19:38:32 GMT

I would like to have the aggregated cell values be derived by the "Mode" of the original input cells. The options for the aggregate tool include Min., Max, Median, Mean, and Sum., but there is no Mode option.-Andy

I was thinking about Block Statistics, but it turns out the Resample tool has a MAJORITY option.

Re: Aggregate raster doesn't have "Mode" function

AndrewOrr — Sun, 20 Feb 2011 18:38:17 GMT

Thank you for the help.
Curtis, your solution solved my problem. I was not aware of the resample function and sure enough it seems to have done exactly what I was looking for.

Whuber:
The reason I need to use a "majority" or mode function is because I am trying to determine the predominant set of slopes for a larger cell size that I've created. So the use of the tool is such that I have a 30m grid size of slopes calculated from a DEM and I wanted to create a 1609 meter set of cells which have the mode of the 30m cells it is being derived from. I believe this is the best approximation method for my use. If a sample of land has many values that are 2 degrees slope I want it to represent that rather than the whole average of all the cells the larger cell is being derived from. I hope that makes sense.

Thanks again for your help,
-Andy

Re: Aggregate raster doesn't have "Mode" function

AndrewOrr — Sun, 06 Mar 2011 05:32:27 GMT

Bill,
Thank you for your detailed reply. That's a very informative bit of information you presented. Much thanks.

After preforming the mode agg. on the data, I realized that the tool had several miss-labeled cells. The small-sized cells would be primarily high-slope values and yet the re-sample tool with mode selected gave me the larger, agg. cell displaying as a low-slope value. Very much an incorrect answer.

I believe my next option will be to use the aggregate tool and look at some of the functions it offers and see how to they compare to one-another.

Thanks all for your time,
-Andy