Python numpy.nonzero() Examples

def vis_parsing(img, parsing, colormap, show_segms=True):
    """Visualizes a single binary parsing."""
    img = img.astype(np.float32)
    idx = np.nonzero(parsing)

    parsing_alpha = cfg.VIS.SHOW_PARSS.PARSING_ALPHA
    colormap = colormap_utils.dict2array(colormap)
    parsing_color = colormap[parsing.astype(np.int)]

    border_color = cfg.VIS.SHOW_PARSS.BORDER_COLOR
    border_thick = cfg.VIS.SHOW_PARSS.BORDER_THICK

    img[idx[0], idx[1], :] *= 1.0 - parsing_alpha
    # img[idx[0], idx[1], :] += alpha * parsing_color
    img += parsing_alpha * parsing_color

    if cfg.VIS.SHOW_PARSS.SHOW_BORDER and not show_segms:
        _, contours, _ = cv2.findContours(parsing.copy(), cv2.RETR_CCOMP, cv2.CHAIN_APPROX_NONE)
        cv2.drawContours(img, contours, -1, border_color, border_thick, cv2.LINE_AA)

    return img.astype(np.uint8) 

def vis_mask(img, mask, bbox_color, show_parss=False):
    """Visualizes a single binary mask."""
    img = img.astype(np.float32)
    idx = np.nonzero(mask)

    border_color = cfg.VIS.SHOW_SEGMS.BORDER_COLOR
    border_thick = cfg.VIS.SHOW_SEGMS.BORDER_THICK

    mask_color = bbox_color if cfg.VIS.SHOW_SEGMS.MASK_COLOR_FOLLOW_BOX else _WHITE
    mask_color = np.asarray(mask_color)
    mask_alpha = cfg.VIS.SHOW_SEGMS.MASK_ALPHA

    _, contours, _ = cv2.findContours(mask.copy(), cv2.RETR_CCOMP, cv2.CHAIN_APPROX_NONE)
    if cfg.VIS.SHOW_SEGMS.SHOW_BORDER:
        cv2.drawContours(img, contours, -1, border_color, border_thick, cv2.LINE_AA)

    if cfg.VIS.SHOW_SEGMS.SHOW_MASK and not show_parss:
        img[idx[0], idx[1], :] *= 1.0 - mask_alpha
        img[idx[0], idx[1], :] += mask_alpha * mask_color

    return img.astype(np.uint8) 

def trim_pixel_list(pixel_locations, active_pixels):
    ''' Trims the list of pixel locations to only the active pixels.

    :param tuple pixel_locations: A tuple of two lists representing the x and y
        coordinates of the locations of a set of pixels (i.e. the output of
        numpy.nonzero(valid_pixels) where valid_pixels is a 2D boolean array
        representing the pixel locations)
    :param list active_pixels: A list the same length as the x and y coordinate
        lists within pixel_locations representing whether a pixel location
        should be represented in the mask or not

    :returns: A tuple of two lists representing the x and y coordinates of the
        locations of active pixels
    '''
    active_pixels = numpy.nonzero(active_pixels)[0]
    return (pixel_locations[0][active_pixels],
            pixel_locations[1][active_pixels]) 

def _step1(state):
    """Steps 1 and 2 in the Wikipedia page."""

    # Step 1: For each row of the matrix, find the smallest element and
    # subtract it from every element in its row.
    state.C -= state.C.min(axis=1)[:, np.newaxis]
    # Step 2: Find a zero (Z) in the resulting matrix. If there is no
    # starred zero in its row or column, star Z. Repeat for each element
    # in the matrix.
    for i, j in zip(*np.nonzero(state.C == 0)):
        if state.col_uncovered[j] and state.row_uncovered[i]:
            state.marked[i, j] = 1
            state.col_uncovered[j] = False
            state.row_uncovered[i] = False

    state._clear_covers()
    return _step3 

def rollout_iterator(self):
        """
        Iterate through all the rollouts in the dataset sequentially
        """
        end_indices = np.nonzero(self._dones)[0] + 1

        states = np.asarray(self._states)
        actions = np.asarray(self._actions)
        next_states = np.asarray(self._next_states)
        rewards = np.asarray(self._rewards)
        dones = np.asarray(self._dones)

        start_idx = 0
        for end_idx in end_indices:
            indices = np.arange(start_idx, end_idx)
            yield states[indices], actions[indices], next_states[indices], rewards[indices], dones[indices]
            start_idx = end_idx 

def prune_non_overlapping_boxes(boxlist1, boxlist2, minoverlap=0.0):
  """Prunes the boxes in boxlist1 that overlap less than thresh with boxlist2.

  For each box in boxlist1, we want its IOA to be more than minoverlap with
  at least one of the boxes in boxlist2. If it does not, we remove it.

  Args:
    boxlist1: BoxList holding N boxes.
    boxlist2: BoxList holding M boxes.
    minoverlap: Minimum required overlap between boxes, to count them as
                overlapping.

  Returns:
    A pruned boxlist with size [N', 4].
  """
  intersection_over_area = ioa(boxlist2, boxlist1)  # [M, N] tensor
  intersection_over_area = np.amax(intersection_over_area, axis=0)  # [N] tensor
  keep_bool = np.greater_equal(intersection_over_area, np.array(minoverlap))
  keep_inds = np.nonzero(keep_bool)[0]
  new_boxlist1 = gather(boxlist1, keep_inds)
  return new_boxlist1 

def random_iterator(self, batch_size):
        """
        Iterate once through all (s, a, r, s') in batches in a random order
        """
        all_indices = np.nonzero(np.logical_not(self._dones))[0]
        np.random.shuffle(all_indices)

        states = np.asarray(self._states)
        actions = np.asarray(self._actions)
        next_states = np.asarray(self._next_states)
        rewards = np.asarray(self._rewards)
        dones = np.asarray(self._dones)

        i = 0
        while i < len(all_indices):
            indices = all_indices[i:i+batch_size]

            yield states[indices], actions[indices], next_states[indices], rewards[indices], dones[indices]

            i += batch_size

    ###############
    ### Logging ###
    ############### 

def plot_force_arrows(self, f):
        """Add arrows to the plot for each force."""
        arrowprops = {"arrowstyle": "->", "connectionstyle": "arc3",
            "lw": "2", "color": 0}
        cmap = plt.cm.get_cmap("hsv", f.shape[1] + 1)
        for load_i in range(f.shape[1]):
            nz = np.nonzero(f[:, load_i])
            arrowprops["color"] = cmap(load_i)
            for i in range(nz[0].shape[0]):
                x, y = id_to_xy(nz[0][i] // 2, self.nelx, self.nely)
                x = max(min(x, self.nelx - 1), 0)
                y = max(min(y, self.nely - 1), 0)
                z = int(nz[0][i] % 2)
                mag = -50 * f[nz[0][i], load_i]
                self.ax.annotate("", xy=(x, y), xycoords="data",
                    xytext = (0 if z else mag, mag if z else 0),
                    textcoords="offset points", arrowprops=arrowprops) 

def log(self):
        end_idxs = np.nonzero(self._dones)[0] + 1

        returns = []

        start_idx = 0
        for end_idx in end_idxs:
            rewards = self._rewards[start_idx:end_idx]
            returns.append(np.sum(rewards))

            start_idx = end_idx

        logger.record_tabular('ReturnAvg', np.mean(returns))
        logger.record_tabular('ReturnStd', np.std(returns))
        logger.record_tabular('ReturnMin', np.min(returns))
        logger.record_tabular('ReturnMax', np.max(returns))

##################
### Tensorflow ###
################## 

def prune_non_overlapping_boxes(boxlist1, boxlist2, minoverlap=0.0):
  """Prunes the boxes in boxlist1 that overlap less than thresh with boxlist2.

  For each box in boxlist1, we want its IOA to be more than minoverlap with
  at least one of the boxes in boxlist2. If it does not, we remove it.

  Args:
    boxlist1: BoxList holding N boxes.
    boxlist2: BoxList holding M boxes.
    minoverlap: Minimum required overlap between boxes, to count them as
                overlapping.

  Returns:
    A pruned boxlist with size [N', 4].
  """
  intersection_over_area = ioa(boxlist2, boxlist1)  # [M, N] tensor
  intersection_over_area = np.amax(intersection_over_area, axis=0)  # [N] tensor
  keep_bool = np.greater_equal(intersection_over_area, np.array(minoverlap))
  keep_inds = np.nonzero(keep_bool)[0]
  new_boxlist1 = gather(boxlist1, keep_inds)
  return new_boxlist1 

def pred_to_dict(text, pred, prob):
    res = {"company": ("", 0), "date": ("", 0), "address": ("", 0), "total": ("", 0)}
    keys = list(res.keys())

    seps = [0] + (numpy.nonzero(numpy.diff(pred))[0] + 1).tolist() + [len(pred)]
    for i in range(len(seps) - 1):
        pred_class = pred[seps[i]] - 1
        if pred_class == -1:
            continue

        new_key = keys[pred_class]
        new_prob = prob[seps[i] : seps[i + 1]].max()
        if new_prob > res[new_key][1]:
            res[new_key] = (text[seps[i] : seps[i + 1]], new_prob)

    return {k: regex.sub(r"[\t\n]", " ", v[0].strip()) for k, v in res.items()} 

def _complexity_dimension(signal, delay=1, dimension_max=20, method="afnn", R=10.0, A=2.0):

    # Initalize vectors
    if isinstance(dimension_max, int):
        dimension_seq = np.arange(1, dimension_max + 1)
    else:
        dimension_seq = np.array(dimension_max)

    # Method
    method = method.lower()
    if method in ["afnn"]:
        E, Es = _embedding_dimension_afn(signal, dimension_seq=dimension_seq, delay=delay, show=False)
        E1 = E[1:] / E[:-1]
        E2 = Es[1:] / Es[:-1]
        min_dimension = [i for i, x in enumerate(E1 >= 0.85 * np.max(E1)) if x][0] + 1
        optimize_indices = [E1, E2]
        return dimension_seq, optimize_indices, min_dimension

    if method in ["fnn"]:
        f1, f2, f3 = _embedding_dimension_ffn(signal, dimension_seq=dimension_seq, delay=delay, R=R, A=A)
        min_dimension = [i for i, x in enumerate(f3 <= 1.85 * np.min(f3[np.nonzero(f3)])) if x][0]
        optimize_indices = [f1, f2, f3]
        return dimension_seq, optimize_indices, min_dimension
    else:
        raise ValueError("NeuroKit error: complexity_dimension(): 'method' not recognized.") 

def _fractal_correlation(signal, r_vals, dist):
    """References
    -----------
    - `nolds <https://github.com/CSchoel/nolds/blob/master/nolds/measures.py>`_
    """
    n = len(signal)

    corr = np.zeros(len(r_vals))
    for i, r in enumerate(r_vals):
        corr[i] = 1 / (n * (n - 1)) * np.sum(dist < r)

    # filter zeros from csums
    nonzero = np.nonzero(corr)[0]
    r_vals = r_vals[nonzero]
    corr = corr[nonzero]

    return r_vals, corr 

def pixel_list_to_array(pixel_locations, shape):
    ''' Transforms a list of pixel locations into a 2D array.

    :param tuple pixel_locations: A tuple of two lists representing the x and y
        coordinates of the locations of a set of pixels (i.e. the output of
        numpy.nonzero(valid_pixels) where valid_pixels is a 2D boolean array
        representing the pixel locations)
    :param list active_pixels: A list the same length as the x and y coordinate
        lists within pixel_locations representing whether a pixel location
        should be represented in the mask or not
    :param tuple shape: The shape of the output array consisting of a tuple
        of (height, width)

    :returns: A 2-D boolean array representing active pixels
    '''
    mask = numpy.zeros(shape, dtype=numpy.bool)
    mask[pixel_locations] = True

    return mask 

def plot_force_arrows(self, f):
        """Add arrows to the plot for each force."""
        arrowprops = {"arrowstyle": "->", "connectionstyle": "arc3",
            "lw": "2", "color": 0}
        cmap = plt.cm.get_cmap("hsv", f.shape[1] + 1)
        for load_i in range(f.shape[1]):
            nz = np.nonzero(f[:, load_i])
            arrowprops["color"] = cmap(load_i)
            for i in range(nz[0].shape[0]):
                x, y = id_to_xy(nz[0][i] // 2, self.nelx, self.nely)
                x = max(min(x, self.nelx - 1), 0)
                y = max(min(y, self.nely - 1), 0)
                z = int(nz[0][i] % 2)
                mag = -50 * f[nz[0][i], load_i]
                self.ax.annotate("", xy=(x, y), xycoords="data",
                    xytext = (0 if z else mag, mag if z else 0),
                    textcoords="offset points", arrowprops=arrowprops) 

def _uniform_weight_alpha(sum_masked_arrays, output_datatype):
    '''Calculates the cumulative mask of a list of masked array

    Input:
        sum_masked_arrays (list of numpy masked arrays): The list of
            masked arrays to find the cumulative mask of, each element
            represents one band.
            (sums_masked_array.mask has a 1 for a no data pixel and
            a 0 otherwise)
        output_datatype (numpy datatype): The output datatype

    Output:
        output_alpha (numpy uint16 array): The output mask
            (0 for a no data pixel, uint16 max value otherwise)
    '''

    output_alpha = numpy.ones(sum_masked_arrays[0].shape)
    for band_sum_masked_array in sum_masked_arrays:
        output_alpha[numpy.nonzero(band_sum_masked_array.mask == 1)] = 0

    output_alpha = output_alpha.astype(output_datatype) * \
        numpy.iinfo(output_datatype).max

    return output_alpha 

def create_pixel_plots(candidate_path, reference_path, base_name,
                       last_band_alpha=False, limits=None, custom_alpha=None):
    c_ds, c_alpha, c_band_count = _open_image_and_get_info(
        candidate_path, last_band_alpha)
    r_ds, r_alpha, r_band_count = _open_image_and_get_info(
        reference_path, last_band_alpha)

    _assert_consistent(c_alpha, r_alpha, c_band_count, r_band_count)

    if custom_alpha != None:
        combined_alpha = custom_alpha
    else:
        combined_alpha = numpy.logical_and(c_alpha, r_alpha)
    valid_pixels = numpy.nonzero(combined_alpha)

    for band_no in range(1, c_band_count + 1):
        c_band = gimage.read_single_band(c_ds, band_no)
        r_band = gimage.read_single_band(r_ds, band_no)
        file_name = '{}_{}.png'.format(base_name, band_no)
        display.plot_pixels(file_name, c_band[valid_pixels],
                            r_band[valid_pixels], limits) 

def create_all_bands_histograms(candidate_path, reference_path, base_name,
                                last_band_alpha=False,
                                color_order=['b', 'g', 'r', 'y'],
                                x_limits=None, y_limits=None):
    c_gimg = gimage.load(candidate_path, last_band_alpha=last_band_alpha)
    r_gimg = gimage.load(reference_path, last_band_alpha=last_band_alpha)

    gimage.check_comparable([c_gimg, r_gimg])

    combined_alpha = numpy.logical_and(c_gimg.alpha, r_gimg.alpha)
    valid_pixels = numpy.nonzero(combined_alpha)

    file_name = '{}_histograms.png'.format(base_name)
    display.plot_histograms(
        file_name,
        [c_band[valid_pixels] for c_band in c_gimg.bands],
        [r_band[valid_pixels] for r_band in r_gimg.bands],
        color_order, x_limits, y_limits) 

def generate_ols_regression(candidate_band, reference_band, pif_mask):
    ''' Performs PCA analysis on the valid pixels and filters according
    to the distance from the principle eigenvector.

    :param array candidate_band: A 2D array representing the image data of the
                                 candidate band
    :param array reference_band: A 2D array representing the image data of the
                                  reference image
    :param array pif_mask: A 2D array representing the PIF pixels in the images

    :returns: A LinearTransformation object (gain and offset)
    '''
    candidate_pifs = candidate_band[numpy.nonzero(pif_mask)]
    reference_pifs = reference_band[numpy.nonzero(pif_mask)]

    return generate_ols_regression_pixel_list(candidate_pifs, reference_pifs) 

def _get_counts(self, timestamp=None, all_outcomes=False):
        """
        Returns this row's sequence of "repetition counts", that is, the number of
        repetitions of each outcome label in the `outcomes` list, or
        equivalently, each outcome label index in this rows `.oli` member.
        """
        #Note: when all_outcomes == False we don't add outcome labels that
        # aren't present for any of this row's elements (i.e. the #summed
        # is zero)
        cntDict = _ld.OutcomeLabelDict()
        if timestamp is not None:
            tslc = _np.where(_np.isclose(self.time, timestamp))[0]
        else: tslc = slice(None)

        if self.reps is None:
            for ol, i in self.dataset.olIndex.items():
                cnt = float(_np.count_nonzero(_np.equal(self.oli[tslc], i)))
                if all_outcomes or cnt > 0: cntDict[ol] = cnt
        else:
            for ol, i in self.dataset.olIndex.items():
                inds = _np.nonzero(_np.equal(self.oli[tslc], i))[0]
                if all_outcomes or len(inds) > 0:
                    cntDict[ol] = float(sum(self.reps[tslc][inds]))
        return cntDict 

def meshresample(pointnp_px3, facenp_fx3, edgenp_ex2):
    p1 = pointnp_px3[edgenp_ex2[:, 0], :]
    p2 = pointnp_px3[edgenp_ex2[:, 1], :]
    pmid = (p1 + p2) / 2
    point2np_px3 = np.concatenate((pointnp_px3, pmid), axis=0)
    
    # delete f
    # add 4 new faces
    face2np_fx3 = []
    pnum = np.max(facenp_fx3) + 1
    for f in facenp_fx3:
        p1, p2, p3 = f
        p12 = (edgenp_ex2 == (min(p1, p2), max(p1, p2))).all(axis=1).nonzero()[0] + pnum
        p23 = (edgenp_ex2 == (min(p2, p3), max(p2, p3))).all(axis=1).nonzero()[0] + pnum
        p31 = (edgenp_ex2 == (min(p3, p1), max(p3, p1))).all(axis=1).nonzero()[0] + pnum
        face2np_fx3.append([p1, p12, p31])
        face2np_fx3.append([p12, p2, p23])
        face2np_fx3.append([p31, p23, p3])
        face2np_fx3.append([p12, p23, p31])
    face2np_fx3 = np.array(face2np_fx3, dtype=np.int64)
    return point2np_px3, face2np_fx3 

def GetItemPixels(self, I):
        '''
        Locates items that should be picked up on the screen
        '''
        ws = [8, 14]
        D1 = np.abs(I - np.array([10.8721,  12.8995,  13.9932])).sum(axis = 2) < 15
        D2 = np.abs(I - np.array([118.1302, 116.0938, 106.9063])).sum(axis = 2) < 76
        R1 = view_as_windows(D1, ws, ws).sum(axis = (2, 3))
        R2 = view_as_windows(D2, ws, ws).sum(axis = (2, 3))
        FR = ((R1 + R2 / np.prod(ws)) >= 1.0) & (R1 > 10) & (R2 > 10)
        PL = np.transpose(np.nonzero(FR)) * np.array(ws)
        if len(PL) <= 0:
            return []
        bc = Birch(threshold = 50, n_clusters = None)
        bc.fit(PL)
        return bc.subcluster_centers_ 

def test_return_correct_matches_with_default_thresholds(self):

    def graph_fn(similarity_matrix):
      matcher = argmax_matcher.ArgMaxMatcher(matched_threshold=None)
      match = matcher.match(similarity_matrix)
      matched_cols = match.matched_column_indicator()
      unmatched_cols = match.unmatched_column_indicator()
      match_results = match.match_results
      return (matched_cols, unmatched_cols, match_results)

    similarity = np.array([[1., 1, 1, 3, 1],
                           [2, -1, 2, 0, 4],
                           [3, 0, -1, 0, 0]], dtype=np.float32)
    expected_matched_rows = np.array([2, 0, 1, 0, 1])
    (res_matched_cols, res_unmatched_cols,
     res_match_results) = self.execute(graph_fn, [similarity])

    self.assertAllEqual(res_match_results[res_matched_cols],
                        expected_matched_rows)
    self.assertAllEqual(np.nonzero(res_matched_cols)[0], [0, 1, 2, 3, 4])
    self.assertFalse(np.all(res_unmatched_cols)) 

def test_return_correct_matches_with_matched_threshold(self):

    def graph_fn(similarity):
      matcher = argmax_matcher.ArgMaxMatcher(matched_threshold=3.)
      match = matcher.match(similarity)
      matched_cols = match.matched_column_indicator()
      unmatched_cols = match.unmatched_column_indicator()
      match_results = match.match_results
      return (matched_cols, unmatched_cols, match_results)

    similarity = np.array([[1, 1, 1, 3, 1],
                           [2, -1, 2, 0, 4],
                           [3, 0, -1, 0, 0]], dtype=np.float32)
    expected_matched_cols = np.array([0, 3, 4])
    expected_matched_rows = np.array([2, 0, 1])
    expected_unmatched_cols = np.array([1, 2])

    (res_matched_cols, res_unmatched_cols,
     match_results) = self.execute(graph_fn, [similarity])
    self.assertAllEqual(match_results[res_matched_cols], expected_matched_rows)
    self.assertAllEqual(np.nonzero(res_matched_cols)[0], expected_matched_cols)
    self.assertAllEqual(np.nonzero(res_unmatched_cols)[0],
                        expected_unmatched_cols) 

def test_return_correct_matches_with_matched_and_unmatched_threshold(self):

    def graph_fn(similarity):
      matcher = argmax_matcher.ArgMaxMatcher(matched_threshold=3.,
                                             unmatched_threshold=2.)
      match = matcher.match(similarity)
      matched_cols = match.matched_column_indicator()
      unmatched_cols = match.unmatched_column_indicator()
      match_results = match.match_results
      return (matched_cols, unmatched_cols, match_results)

    similarity = np.array([[1, 1, 1, 3, 1],
                           [2, -1, 2, 0, 4],
                           [3, 0, -1, 0, 0]], dtype=np.float32)
    expected_matched_cols = np.array([0, 3, 4])
    expected_matched_rows = np.array([2, 0, 1])
    expected_unmatched_cols = np.array([1])  # col 2 has too high maximum val

    (res_matched_cols, res_unmatched_cols,
     match_results) = self.execute(graph_fn, [similarity])
    self.assertAllEqual(match_results[res_matched_cols], expected_matched_rows)
    self.assertAllEqual(np.nonzero(res_matched_cols)[0], expected_matched_cols)
    self.assertAllEqual(np.nonzero(res_unmatched_cols)[0],
                        expected_unmatched_cols) 

def test_return_correct_matches_unmatched_row_while_using_force_match(self):
    def graph_fn(similarity):
      matcher = argmax_matcher.ArgMaxMatcher(matched_threshold=3.,
                                             unmatched_threshold=2.,
                                             force_match_for_each_row=True)
      match = matcher.match(similarity)
      matched_cols = match.matched_column_indicator()
      unmatched_cols = match.unmatched_column_indicator()
      match_results = match.match_results
      return (matched_cols, unmatched_cols, match_results)

    similarity = np.array([[1, 1, 1, 3, 1],
                           [-1, 0, -2, -2, -1],
                           [3, 0, -1, 2, 0]], dtype=np.float32)
    expected_matched_cols = np.array([0, 1, 3])
    expected_matched_rows = np.array([2, 1, 0])
    expected_unmatched_cols = np.array([2, 4])  # col 2 has too high max val

    (res_matched_cols, res_unmatched_cols,
     match_results) = self.execute(graph_fn, [similarity])
    self.assertAllEqual(match_results[res_matched_cols], expected_matched_rows)
    self.assertAllEqual(np.nonzero(res_matched_cols)[0], expected_matched_cols)
    self.assertAllEqual(np.nonzero(res_unmatched_cols)[0],
                        expected_unmatched_cols) 

def prune_non_overlapping_boxes(boxlist1, boxlist2, minoverlap=0.0):
  """Prunes the boxes in boxlist1 that overlap less than thresh with boxlist2.

  For each box in boxlist1, we want its IOA to be more than minoverlap with
  at least one of the boxes in boxlist2. If it does not, we remove it.

  Args:
    boxlist1: BoxList holding N boxes.
    boxlist2: BoxList holding M boxes.
    minoverlap: Minimum required overlap between boxes, to count them as
                overlapping.

  Returns:
    A pruned boxlist with size [N', 4].
  """
  intersection_over_area = ioa(boxlist2, boxlist1)  # [M, N] tensor
  intersection_over_area = np.amax(intersection_over_area, axis=0)  # [N] tensor
  keep_bool = np.greater_equal(intersection_over_area, np.array(minoverlap))
  keep_inds = np.nonzero(keep_bool)[0]
  new_boxlist1 = gather(boxlist1, keep_inds)
  return new_boxlist1 

def info_gain_numeric(x, y, accuracy):
    x_unique = list(np.unique(x))
    if len(x_unique) == 1:
        return None
    indices = x.argsort()  # sort numeric attribute
    x, y = x[indices], y[indices]  # save sorted features with sorted labels

    right_dist = np.bincount(y)
    dummy_class = np.array([len(right_dist)])
    class_indices = right_dist.nonzero()[0]
    right_dist = right_dist[class_indices]
    left_dist = np.zeros(len(class_indices))

    diffs = np.nonzero(y[:-1] != y[1:])[0] + 1  # different neighbor classes have value True
    if accuracy > 0:
        diffs = np.array([diffs[i] for i in range(1, len(diffs)) if diffs[i] - diffs[i - 1] > accuracy],
                         dtype=np.int32) if len(diffs) > 15 else diffs
    intervals = np.array((np.concatenate(([0], diffs[:-1])), diffs)).T
    if len(diffs) < 2:
        return None

    max_ig, max_i, max_j = 0, 0, 0
    prior_h = h(right_dist)  # calculate prior entropy

    for i, j in intervals:
        dist = np.bincount(np.concatenate((dummy_class, y[i:j])))[class_indices]
        left_dist += dist
        right_dist -= dist
        coef = np.true_divide((np.sum(left_dist), np.sum(right_dist)), len(y))
        ig = prior_h - np.dot(coef, [h(left_dist[left_dist.nonzero()]), h(right_dist[right_dist.nonzero()])])
        if ig > max_ig:
            max_ig, max_i, max_j = ig, i, j

    if x[max_i] == x[max_j]:
        ind = x_unique.index(x[max_i])
        mean = np.float32(np.mean((x_unique[1 if ind == 0 else ind - 1], x_unique[ind])))
    else:
        mean = np.float32(np.mean((x[max_i], x[max_j])))

    return float(max_ig), [mean, mean] 

def clip_to_window(boxlist, window):
  """Clip bounding boxes to a window.

  This op clips input bounding boxes (represented by bounding box
  corners) to a window, optionally filtering out boxes that do not
  overlap at all with the window.

  Args:
    boxlist: BoxList holding M_in boxes
    window: a numpy array of shape [4] representing the
            [y_min, x_min, y_max, x_max] window to which the op
            should clip boxes.

  Returns:
    a BoxList holding M_out boxes where M_out <= M_in
  """
  y_min, x_min, y_max, x_max = np.array_split(boxlist.get(), 4, axis=1)
  win_y_min = window[0]
  win_x_min = window[1]
  win_y_max = window[2]
  win_x_max = window[3]
  y_min_clipped = np.fmax(np.fmin(y_min, win_y_max), win_y_min)
  y_max_clipped = np.fmax(np.fmin(y_max, win_y_max), win_y_min)
  x_min_clipped = np.fmax(np.fmin(x_min, win_x_max), win_x_min)
  x_max_clipped = np.fmax(np.fmin(x_max, win_x_max), win_x_min)
  clipped = np_box_list.BoxList(
      np.hstack([y_min_clipped, x_min_clipped, y_max_clipped, x_max_clipped]))
  clipped = _copy_extra_fields(clipped, boxlist)
  areas = area(clipped)
  nonzero_area_indices = np.reshape(np.nonzero(np.greater(areas, 0.0)),
                                    [-1]).astype(np.int32)
  return gather(clipped, nonzero_area_indices) 

def get_sequence_with_singing_indices(full_sequence):

    signal_magnitude = np.abs(full_sequence)

    chunk_length = 800

    chunks_energies = []
    for i in xrange(0, len(signal_magnitude), chunk_length):
        chunks_energies.append(np.mean(signal_magnitude[i:i + chunk_length]))

    threshold = np.max(chunks_energies) * .1
    chunks_energies = np.asarray(chunks_energies)
    chunks_energies[np.where(chunks_energies < threshold)] = 0
    onsets = np.zeros(len(chunks_energies))
    onsets[np.nonzero(chunks_energies)] = 1
    onsets = np.diff(onsets)

    start_ind = np.squeeze(np.where(onsets == 1))
    finish_ind = np.squeeze(np.where(onsets == -1))

    if finish_ind[0] < start_ind[0]:
        finish_ind = finish_ind[1:]

    if start_ind[-1] > finish_ind[-1]:
        start_ind = start_ind[:-1]

    indices_inici_final = np.insert(finish_ind, np.arange(len(start_ind)), start_ind)

    return np.squeeze((np.asarray(indices_inici_final) + 1) * chunk_length)