[yt-users] define a general derived field from other fields

[gso at physics.ucsd.edu]

Hi all,

I'm currently trying to find a way to define a clumping factor by giving
this formula (for unigrid simulation no AMR):

def _HIIClumpingFactorParts(data):
    square_HIIdensity = (data["HII_Density"]**2).sum()
    sum_HIIdensity = (data["HII_Density"]).sum()
    return square_HIIdensity, sum_HIIdensity

def _HIIMultiplyParts(data, square_HIIdensity, sum_HIIdensity):
    return
data.quantities["TotalQuantity"]("Ones")[0]*square_HIIdensity.sum()/sum_HIIdensity.sum()**2

add_quantity("HIIClumpingFactor", function=_HIIClumpingFactorParts,
combine_function=_HIIMultiplyParts, n_ret = 2)

I was wondering how I can generalize this formula to be used with
different fields if I want to say get the clumping factor of HI_Density,
or HeI_Density, Dark_Matter_Density etc?

From
G.S.