arcgis-10.0arcgis-desktopfield-calculatorpython-parser
I need to calculate the max M value for a line feature using Python in ArcGIS 10 Field Calculator but I cannot figure it out. In 9.3 I used the follow VBA expression…
**Pre-Logic VBA Script Code:**
dim m as imcollection
set m = [shape]
dim d as double
d = m.mmax
**EndStation =:**
d
For VB, something like this should work, I think:
Pre-logic script code:
Dim f2 As Double
If [grid_code] = 1 Then
f2 = 2
ElseIf [grid_code] = 2 Then
f2 = 3.5
End If
asp_code =
f2
In Python, I think it would be something like this (though I don't have ArcGIS 10 so I can't check):
Pre-logic script code:
def my_func(my_field):
if my_field == 1:
f2 = 2
elif my_field == 2:
f2 = 3.5
return f2
asp_code =
my_func(!grid_code!)
The error message saying that the "calculated value is invalid" is a bit strange. Perhaps double-check that your asp_code field is of float or double data type (not integer), and that you have all of the options in the grid_code field covered by your if statements? Sorry if that's too obvious, but it's all I can think of at the moment. Good luck!
I think the problem lies with your statement:
def !gridcode! (value):
is incorrect, see http://resources.arcgis.com/en/help/main/10.1/index.html#//00170000004s000000
def something(value):
It's hard to read what you've got there but I think this is it:
Full expression:
def TextValue(FromCode):
if FromCode > 0 and FromCode < 50:
return "0 - 50 cm from the surface"
elif FromCode < 150:
return "101 - 150 cm"
elif FromCode < 200:
return "151 - 200 cm"
elif FromCode < 250:
return "201 - 250 cm"
elif FromCode < 1000:
return "251 - 1000 cm"
else:
return "N/A"
This will populate the text that is in the legend using the GRIDCODE as the numeric source.
Best Answer
use field calc to return the MAX M measures:
use field calc to return the Min M measures:
you can then calculate the M-length of the line using subtraction.