Utils_Bashivan.py

'''
Created by Pouya bashivan
This code has been created by p. bashivan source : https://github.com/pbashivan/EEGLearn
'''


__author__ = 'Pouya Bashivan'


import numpy as np
np.random.seed(123)
import scipy.io

from scipy.interpolate import griddata
from sklearn.preprocessing import scale
import math as m
from sklearn.decomposition import PCA

def azim_proj(pos):
    """
    Computes the Azimuthal Equidistant Projection of input point in 3D Cartesian Coordinates.
    Imagine a plane being placed against (tangent to) a globe. If
    a light source inside the globe projects the graticule onto
    the plane the result would be a planar, or azimuthal, map
    projection.
    :param pos: position in 3D Cartesian coordinates
    :return: projected coordinates using Azimuthal Equidistant Projection
    """
    [r, elev, az] = cart2sph(pos[0], pos[1], pos[2])
    return pol2cart(az, m.pi / 2 - elev)

def cart2sph(x, y, z):
    """
    Transform Cartesian coordinates to spherical
    :param x: X coordinate
    :param y: Y coordinate
    :param z: Z coordinate
    :return: radius, elevation, azimuth
    """
    x2_y2 = x**2 + y**2
    r = m.sqrt(x2_y2 + z**2)                    # r
    elev = m.atan2(z, m.sqrt(x2_y2))            # Elevation
    az = m.atan2(y, x)                          # Azimuth
    return r, elev, az


def pol2cart(theta, rho):
    """
    Transform polar coordinates to Cartesian
    :param theta: angle value
    :param rho: radius value
    :return: X, Y
    """
    return rho * m.cos(theta), rho * m.sin(theta)

def gen_images(locs, features, n_gridpoints, normalize=True,
               augment=False, pca=False, std_mult=0.1, n_components=2, edgeless=False):
    """
    Generates EEG images given electrode locations in 2D space and multiple feature values for each electrode
    :param locs: An array with shape [n_electrodes, 2] containing X, Y
                        coordinates for each electrode.
    :param features: Feature matrix as [n_samples, n_features]
                                Features are as columns.
                                Features corresponding to each frequency band are concatenated.
                                (alpha1, alpha2, ..., beta1, beta2,...)
    :param n_gridpoints: Number of pixels in the output images
    :param normalize:   Flag for whether to normalize each band over all samples
    :param augment:     Flag for generating augmented images
    :param pca:         Flag for PCA based data augmentation
    :param std_mult     Multiplier for std of added noise
    :param n_components: Number of components in PCA to retain for augmentation
    :param edgeless:    If True generates edgeless images by adding artificial channels
                        at four corners of the image with value = 0 (default=False).
    :return:            Tensor of size [samples, colors, W, H] containing generated
                        images.
    """
    feat_array_temp = []
    nElectrodes = locs.shape[0]     # Number of electrodes

    # Test whether the feature vector length is divisible by number of electrodes
    assert features.shape[1] % nElectrodes == 0
    n_colors = int(features.shape[1] / nElectrodes)
    for c in range(n_colors):
        feat_array_temp.append(features[:, c * nElectrodes : nElectrodes * (c+1)])
    if augment:
        if pca:
            for c in range(n_colors):
                feat_array_temp[c] = augment_EEG(feat_array_temp[c], std_mult, pca=True, n_components=n_components)
        else:
            for c in range(n_colors):
                feat_array_temp[c] = augment_EEG(feat_array_temp[c], std_mult, pca=False, n_components=n_components)
    n_samples = features.shape[0]

    # Interpolate the values
    grid_x, grid_y = np.mgrid[
                     min(locs[:, 0]):max(locs[:, 0]):n_gridpoints*1j,
                     min(locs[:, 1]):max(locs[:, 1]):n_gridpoints*1j
                     ]
    temp_interp = []
    for c in range(n_colors):
        temp_interp.append(np.zeros([n_samples, n_gridpoints, n_gridpoints]))

    # Generate edgeless images
    if edgeless:
        min_x, min_y = np.min(locs, axis=0)
        max_x, max_y = np.max(locs, axis=0)
        locs = np.append(locs, np.array([[min_x, min_y], [min_x, max_y], [max_x, min_y], [max_x, max_y]]), axis=0)
        for c in range(n_colors):
            feat_array_temp[c] = np.append(feat_array_temp[c], np.zeros((n_samples, 4)), axis=1)

    # Interpolating
    for i in range(n_samples):
        for c in range(n_colors):
            temp_interp[c][i, :, :] = griddata(locs, feat_array_temp[c][i, :], (grid_x, grid_y),
                                               method='cubic', fill_value=np.nan)
        print('Interpolating {0}/{1}\r'.format(i + 1, n_samples), end='\r')

    # Normalizing
    for c in range(n_colors):
        if normalize:
            temp_interp[c][~np.isnan(temp_interp[c])] = \
                scale(temp_interp[c][~np.isnan(temp_interp[c])])
        temp_interp[c] = np.nan_to_num(temp_interp[c])
    return np.swapaxes(np.asarray(temp_interp), 0, 1)     # swap axes to have [samples, colors, W, H]