Source code for nmrsim.firstorder

""""Functions for calculating first-order spectra.

The nmrsim.firstorder module provides the following functions:

* multiplet: performs first-order splitting of a signal into multiple signals.

* first_order_spin_system: provides a peaklist for several nuclei, using the
    same v/J parameters that are used for second-order spin systems.
    See nmrsim.qm for details on these parameters.

from nmrsim.math import reduce_peaks

def _doublet(plist, J):
    Applies a *J* coupling to each signal in a list of (frequency, intensity)
    signals, creating two half-intensity signals at +/- *J*/2.

    plist : [(float, float)...]
        a list of (frequency{Hz}, intensity) tuples.
    J : float
        The coupling constant in Hz.

    [(float, float)...]
        a list of (frequency, intensity) tuples.
    res = []
    for v, i in plist:
        res.append((v - J / 2, i / 2))
        res.append((v + J / 2, i / 2))
    return res

# TODO: consider making the multiplet and nmrsim.Multiplet arguments similar
[docs]def multiplet(signal, couplings): """ Splits a set of signals into first-order multiplets. Parameters --------- signal : (float, float) a (frequency (Hz), intensity) tuple; couplings : [(float, int)...] A list of (*J*, # of nuclei) tuples. The order of the tuples in couplings does not matter. e.g. to split a signal into a *dt, J* = 8, 5 Hz, use: ``couplings = [(8, 2), (5, 3)]`` Returns ------- [(float, float)...] a sorted peaklist for the multiplet that results from splitting the signal by each J. """ res = [signal] for coupling in couplings: for i in range(coupling[1]): res = _doublet(res, coupling[0]) return sorted(reduce_peaks(res))
[docs]def first_order_spin_system(v, J): """ Create a first-order peaklist of several multiplets from the same v/J arguments used for qm calculations. This allows a user to model several multiplets at once, rather than creating each multiplet individually. It also provides a "toggle" where the user, or a higher-level function/class (such as nmrsim.SpinSystem) can decide whether a spin system is modeled as first order or second order. Parameters ---------- v : array-like [float...] an array of frequencies J : 2D array-like (square) a matrix of J coupling constants Returns ------- [(float, float)...] a combined peaklist of signals for all the multiplets in the spin system. """ result = [] for i, v_ in enumerate(v): couplings = ((j, 1) for j in J[i] if j != 0) signal = multiplet((v_, 1), couplings) result += signal return reduce_peaks(sorted(result))