[SOLVED] Human-readable output with DEAP

Human-readable output with DEAP

I am using DEAP to do symbolic regression on a table of data, i.e. finding a function that best fits the data. Unfortunately, I can't find a way of getting the result in human-readable format. For instance, if I do

best_ind = tools.selBest(pop, 1)[0]
print("Best individual is %s" % (best_ind))

my output is likely to look something like

Best individual is add(mul(add(x, 2), div(y, add(x, y))), 1)

but that is difficult for a human to interpret. Is there a way to print the result in a way that looks more like

(x+2)*(y/(x+y))+1

Solution

You can start with using sympy.simplify

import sympy

expr = "Add(x, 2)"
sympy.simplify(expr)  # x + 2

However, sympy wants add, mul etc capitalized. Also You need to translate Div(a, b) to Mul(a, 1/b).

You can do this by changing the primitive.format method like so:

def convert_inverse_prim(prim, args):
    """
    Convert inverse prims according to:
    [Dd]iv(a,b) -> Mul[a, 1/b]
    [Ss]ub(a,b) -> Add[a, -b]
    We achieve this by overwriting the corresponding format method of the sub and div prim.
    """
    prim = copy.copy(prim)
    prim.name = re.sub(r'([A-Z])', lambda pat: pat.group(1).lower(), prim.name)    # lower all capital letters

    converter = {
        'sub': lambda *args_: "Add({}, Mul(-1,{}))".format(*args_),
        'div': lambda *args_: "Mul({}, Pow({}, -1))".format(*args_)
    }
    prim_formatter = converter.get(prim.name, prim.format)

    return prim_formatter(*args)

This code is taken from glyph.