AnsweredAssumed Answered

Problem with conditional statements for Fuzzy membership in Python

Question asked by goodhen on Nov 26, 2016
Latest reply on Nov 27, 2016 by goodhen

Hi, I'm new to Python, and have been having problems with conditional statements. There are two issues:


1) One of my conditions is that anything <5 = 0. When I do this, anything with a negative number returns as 'no data' instead of 0


2) When the returning value refers back to the input raster, the syntax fails. The statement works in Raster Calculator, but it seems like I should be using different syntax in Python, but can't find any documentation about this.



inRas1 = arcpy.Raster(r"C:\Data\WorldClim\Minimum\tmin1.tif")

minA = float(5)
minB = float(15)
maxC = float(23)
maxD = float(27)
divA = (minB - minA)
divB = (maxD - maxC)



The full statement is as follows (line breaks for clarity - not in actual script!):

outCon1 = Con((inRas1 > minB) & (inRas1 < maxC),1, 

Con((inRas1 < minA) & (inRas1 > maxD),0, 

Con((inRas1 > minA) & (inRas1 < minB),(inRas1 – minA)/divA, 

Con((inRas1 > maxC) & (inRas1 < maxD),(maxD - inRas1)/divB))))



I simplified it to this and it worked:

outCon1 = Con((inRas1 > minB) & (inRas1 < maxC),(minA/divA))


However, when I expanded it out to this, it didn't:

outCon1 = Con((inRas1 > minB) & (inRas1 < maxC),(inRas1 – minA)/divA)



So, am I better off doing this as an IF statement? 

Alternatively, do you know a better way of carrying out a trapezoidal membership function? The built in fuzzy tools seem to have everything but this!


Thanks in advance!