discreteModel.py

import numpy as np
import scipy.special as sc

def discreteModel(theta, uvsamples, bins):

    # retrieve inputs
    incl, PA, offset, w = theta
    rin, b = bins
    u, v = uvsamples			# in **lambda** units

    # convert angles to radians
    inclr = np.radians(incl)
    PAr = np.radians(PA)
    offr = offset * np.pi / (180.*3600.)

    # coordinate change to deal with projection, rotation, and shifts
    uprime = (u * np.cos(PAr) + v * np.sin(PAr)) * np.cos(inclr)
    vprime = (-u * np.sin(PAr) + v * np.cos(PAr))
    rho = np.sqrt(uprime**2 + vprime**2) * np.pi / (180.*3600.)

    # re-orient arrays
    rbin = np.concatenate([np.array([rin]), b])
    wbin = np.append(np.concatenate([np.array([0.0]), w]), 0.)
    ww = wbin-np.roll(wbin, -1)
    intensity = np.delete(ww, b.size+1)

    jarg = np.outer(2.*np.pi*rbin, rho)
    jinc = sc.j1(jarg)/jarg

    vis = np.dot(2.*np.pi*rbin**2*intensity, jinc)

    Re_vis = vis * np.cos(-2*np.pi*(u*offr[0] + v*offr[1]))
    Im_vis = vis * np.sin(-2*np.pi*(u*offr[0] + v*offr[1]))

    vis_complex = Re_vis + 1j*Im_vis

    return vis_complex