I"m trying to nest expressions in this raster calculator conditional statement, but I get an error.

This statement works, so I tried to follow it as a template:

Con (IsNull("ras1"),"ras2","ras3")

Separately, this statement works


And I'd love to merge them into one calulation liek this


Where "rasA" is null, return "rasB"-(5+(1/(1+"rasC"))5)("RasD"<=20). Otherwise return "rasB"-(5+(1/(1+"rasC"))5)("RasD"<=500)

I get the error shown below so I'm trying to figure out if Con() requires a layer like the error says or if can I use an expression and I just entered it wrong.

enter image description here

  • 1
    Please remember to place the complete error text in the question as ASCII. This makes it legible on all platforms and available for search by others.
    – Vince
    Mar 26, 2019 at 21:18

1 Answer 1


Your parentheses are incorrect. You have parentheses around both the True and False expressions, i.e:

Con(condition, (true_expression, false_expression))

It should be:

Con(condition, true_expression, false_expression)


Con(IsNull("rasA"), "rasB"-(5+(1/(1+"rasC"))*5)*("RasD"<=20), "rasB"-(5+(1/(1+"rasC"))*5)*("RasD"<=500))


Con(IsNull("rasA"), ("rasB"-(5+(1/(1+"rasC"))*5)*("RasD"<=20)), ("rasB"-(5+(1/(1+"rasC"))*5)*("RasD"<=500)))
  • Parentheses...I always miss some mundane detail like that! point of clarification... in your answer, instead of Con(condition, true_expression, true_expression) should it be Con(condition, true_expression, FALSE_expression) ?
    – Zipper1365
    Mar 27, 2019 at 15:02

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