code/provided/preprocessing.py

import os
import sys
import numpy as np
import json
import joblib
import logging
from os.path import join, dirname
import pickle

def make_delayed(stim, delays, circpad=False):
    """Creates non-interpolated concatenated delayed versions of [stim] with the given [delays] 
    (in samples).
    
    If [circpad], instead of being padded with zeros, [stim] will be circularly shifted.
    """
    nt,ndim = stim.shape
    dstims = []
    for di,d in enumerate(delays):
        dstim = np.zeros((nt, ndim))
        if d<0: ## negative delay
            dstim[:d,:] = stim[-d:,:]
            if circpad:
                dstim[d:,:] = stim[:-d,:]
        elif d>0:
            dstim[d:,:] = stim[:-d,:]
            if circpad:
                dstim[:d,:] = stim[-d:,:]
        else: ## d==0
            dstim = stim.copy()
        dstims.append(dstim)
    return np.hstack(dstims)

def lanczosfun(cutoff, t, window=3):
    """Compute the lanczos function with some cutoff frequency [B] at some time [t].
    [t] can be a scalar or any shaped numpy array.
    If given a [window], only the lowest-order [window] lobes of the sinc function
    will be non-zero.
    """
    t = t * cutoff
    val = window * np.sin(np.pi*t) * np.sin(np.pi*t/window) / (np.pi**2 * t**2)
    val[t==0] = 1.0
    val[np.abs(t)>window] = 0.0
    return val# / (val.sum() + 1e-10)

def lanczosinterp2D(data, oldtime, newtime, window=3, cutoff_mult=1.0, rectify=False):
    """Interpolates the columns of [data], assuming that the i'th row of data corresponds to
    oldtime(i). A new matrix with the same number of columns and a number of rows given
    by the length of [newtime] is returned.
    
    The time points in [newtime] are assumed to be evenly spaced, and their frequency will
    be used to calculate the low-pass cutoff of the interpolation filter.
    
    [window] lobes of the sinc function will be used. [window] should be an integer.
    """
    ## Find the cutoff frequency ##
    cutoff = 1/np.mean(np.diff(newtime)) * cutoff_mult
    # print "Doing lanczos interpolation with cutoff=%0.3f and %d lobes." % (cutoff, window)
    
    ## Build up sinc matrix ##
    sincmat = np.zeros((len(newtime), len(oldtime)))
    for ndi in range(len(newtime)):
        sincmat[ndi,:] = lanczosfun(cutoff, newtime[ndi]-oldtime, window)
    
    if rectify:
        newdata = np.hstack([np.dot(sincmat, np.clip(data, -np.inf, 0)), 
                            np.dot(sincmat, np.clip(data, 0, np.inf))])
    else:
        ## Construct new signal by multiplying the sinc matrix by the data ##
        newdata = np.dot(sincmat, data)

    return newdata

def downsample_word_vectors(stories, word_vectors, wordseqs):
	"""Get Lanczos downsampled word_vectors for specified stories.

	Args:
		stories: List of stories to obtain vectors for.
		word_vectors: Dictionary of {story: <float32>[num_story_words, vector_size]}
        wordseqs: Dictionary of {story: <object>}

	Returns:
		Dictionary of {story: downsampled vectors}
	"""
	downsampled_semanticseqs = dict()
	for story in stories:
		downsampled_semanticseqs[story] = lanczosinterp2D(
			word_vectors[story], wordseqs[story].data_times, 
			wordseqs[story].tr_times, window=3)
	return downsampled_semanticseqs



if __name__ == "__main__":
    raw_stories = pickle.load(open('raw_stories.pkl', 'rb'))