topic How to calculate the right Threshold for flow accumulation using python? in Python Questions https://community.esri.com/t5/python-questions/how-to-calculate-the-right-threshold-for-flow/m-p/335336#M26252 <HTML><HEAD></HEAD><BODY><P>I created a program that generates all the major watersheds that occur on a DEM using a flow accumulation raster. So the only problem that I have, is that my "while loop" depends on the weighted values of the flow accumulation raster. So the condition number I&nbsp;used was 0. This caused my program to create way too many watersheds and most of them I do not need. So I need a threshold number to use as my condition to end the loop. I noticed that I can use the break values that are stored in the classified section in the symbology tab and these values are calculated from a histogram.</P><P><IMG alt="" class="image-1 jive-image j-img-original" src="https://community.esri.com/legacyfs/online/365916_capture9.PNG" style="width: 620px; height: 479px;" /></P><P>This would be an example of a threshold number I would use.&nbsp;Any number below the first break value&nbsp;would give me watersheds that I do not need.&nbsp;What would be the best way to extract this number? I would prefer not to use arcpy.mapping and just have an equation I can use on every Raster to give me a general threshold number in my program. Is there anyway I can use the Maximum,minumum,mean or std value&nbsp;to calculate it using statistics? is there a better&nbsp;threshold number I could use instead?&nbsp;Thank you for your help.</P></BODY></HTML> Mon, 07 Aug 2017 14:56:08 GMT AndrewMartin8 2017-08-07T14:56:08Z How to calculate the right Threshold for flow accumulation using python? https://community.esri.com/t5/python-questions/how-to-calculate-the-right-threshold-for-flow/m-p/335336#M26252 <HTML><HEAD></HEAD><BODY><P>I created a program that generates all the major watersheds that occur on a DEM using a flow accumulation raster. So the only problem that I have, is that my "while loop" depends on the weighted values of the flow accumulation raster. So the condition number I&nbsp;used was 0. This caused my program to create way too many watersheds and most of them I do not need. So I need a threshold number to use as my condition to end the loop. I noticed that I can use the break values that are stored in the classified section in the symbology tab and these values are calculated from a histogram.</P><P><IMG alt="" class="image-1 jive-image j-img-original" src="https://community.esri.com/legacyfs/online/365916_capture9.PNG" style="width: 620px; height: 479px;" /></P><P>This would be an example of a threshold number I would use.&nbsp;Any number below the first break value&nbsp;would give me watersheds that I do not need.&nbsp;What would be the best way to extract this number? I would prefer not to use arcpy.mapping and just have an equation I can use on every Raster to give me a general threshold number in my program. Is there anyway I can use the Maximum,minumum,mean or std value&nbsp;to calculate it using statistics? is there a better&nbsp;threshold number I could use instead?&nbsp;Thank you for your help.</P></BODY></HTML> Mon, 07 Aug 2017 14:56:08 GMT https://community.esri.com/t5/python-questions/how-to-calculate-the-right-threshold-for-flow/m-p/335336#M26252 AndrewMartin8 2017-08-07T14:56:08Z