Field calculator expressions with numpy

danretired

A followup to the recent einsum post, but with a field calculator twist

 

# ---- a numeric field, python expression which uses the shape field to return the longest edge on the perimeter

longest_seg(!Shape!)

# ---- the code block -----

import json
import numpy as np
#
def longest_seg(a):
    """Longest edge"""
    v = json.loads(a.JSON)
    r = v['rings']
    a = np.array(r).squeeze()
    a = a[0] if a.ndim > 2 else a
    diff = a[1:] - a[:-1]
    ret = np.sqrt(np.einsum('ij,ij->i', diff, diff))
    val = np.max(ret)
    return val

 

lines 12-13 :  really? having to convert to JSON format just to get at the array values?