Tailcut finder function and script

lstchain/image/cleaning.py

@@ -1,6 +1,20 @@
+import glob
+import logging
 import numpy as np
+from pathlib import Path
+from lstchain.paths import run_to_dl1_filename
+from lstchain.io.io import dl1_params_lstcam_key, dl1_images_lstcam_key
+from lstchain.io.io import dl1_params_tel_mon_cal_key
+from lstchain.io.config import get_standard_config
+from ctapipe.containers import EventType
+from scipy.stats import median_abs_deviation
 
-__all__ = ['apply_dynamic_cleaning']
+from ctapipe.io import read_table
+__all__ = ['apply_dynamic_cleaning',
+           'find_tailcuts',
+           'pic_th']
+
+log = logging.getLogger(__name__)
 
 
 def apply_dynamic_cleaning(image, signal_pixels, threshold, fraction):
@@ -36,3 +50,236 @@
     mask_dynamic_cleaning = (image >= dynamic_threshold) & signal_pixels
 
     return mask_dynamic_cleaning
+
+
+def find_tailcuts(input_dir, run_number):
+    """
+    This function uses DL1 files to determine tailcuts which are adequate
+    for the bulk of the pixels in a given run. The script also returns the
+    suggested NSB adjustment needed in the "dark-sky" MC to match the data.
+    The function uses the median (for the whole camera, excluding outliers)
+    of the 95% quantile of the pixel charge for pedestal events to deduce the
+    NSB level. It is good to use a large quantile of the pixel charge
+    distribution (vs. e.g. using the median) because what matters for having
+    a realistic noise simulation is the tail on the right-side, i.e. for
+    large pulses.
+    For reasons of stability & simplicity of analysis, we cannot decide the
+    cleaning levels (or the NSB tuning) on a subrun-by-subrun basis. We select
+    values which are more or less valid for the whole run.
+
+    The script will process a subset of the subruns (~10, hardcoded) of the run,
+    distributed uniformly through it.
+
+    Parameters
+    ----------
+    input_dir: `Path`
+        directory where the DL1 files (subrun-wise, i.e., including
+        DL1a) are stored
+
+    run_number : int
+        run number to be processed
+
+    Returns
+    -------
+    additional_nsb_rate : float
+        p.e./ns rate of NSB to be added to "dark MC" to match the noise in the data
+    newconfig : dict
+        cleaning configuration for running the DL1ab stage
+    """
+
+    # subrun-wise dl1 file names:
+    dl1_filenames = Path(input_dir,
+                         run_to_dl1_filename(1, run_number, 0).replace(
+                                 '.0000.h5', '.????.h5'))
+    all_dl1_files = glob.glob(str(dl1_filenames))
+    all_dl1_files.sort()
+
+    # Number of median absolute deviations (mad) away from the median that a
+    # value has to be to be considered an outlier:
+    mad_max = 5  # would exclude 8e-4 of the pdf for a gaussian
+
+    # Minimum number of interleaved pedestals in subrun to proceed with
+    # calculation:
+    min_number_of_ped_events = 100
+
+    # Minimum number of valid pixels to consider the calculation of NSB level
+    # acceptable:
+    min_number_of_valid_pixels = 1000
+
+    # Approx. maximum number of subruns (uniformly distributed through the
+    # run) to be processed:
+    max_number_of_processed_subruns = 10
+    # Keep only ~max_number_of_processed_subruns subruns, distributed
+    # along the run:
+    dl1_files = all_dl1_files[::int(1+len(all_dl1_files) /
+                                    max_number_of_processed_subruns)]
+
+    number_of_pedestals = []
+    median_ped_qt95_pix_charge = []
+
+    for dl1_file in dl1_files:
+        log.info('\nInput file: %s', dl1_file)
+
+        data_parameters = read_table(dl1_file, dl1_params_lstcam_key)
+        event_type_data = data_parameters['event_type'].data
+        pedestal_mask = event_type_data == EventType.SKY_PEDESTAL.value
+
+        num_pedestals = pedestal_mask.sum()
+        if num_pedestals < min_number_of_ped_events:
+            log.warning(f'    Too few interleaved pedestals ('
+                        f'{num_pedestals}) - skipped subrun!')
+            continue
+
+        number_of_pedestals.append(pedestal_mask.sum())
+        data_images = read_table(dl1_file, dl1_images_lstcam_key)
+        data_calib = read_table(dl1_file, dl1_params_tel_mon_cal_key)
+        # data_calib['unusable_pixels'] , indices: (Gain  Calib_id  Pixel)
+
+        # Get the "unusable" flags from the pedcal file:
+        unusable_hg = data_calib['unusable_pixels'][0][0]
+        unusable_lg = data_calib['unusable_pixels'][0][1]
+
+        unreliable_pixels = unusable_hg | unusable_lg
+        if unreliable_pixels.sum() > 0:
+            log.info(f'    Removed {unreliable_pixels.sum()/unreliable_pixels.size:.2%} of pixels '
+                     f'due to unreliable calibration!')
+
+        reliable_pixels = ~unreliable_pixels
+
+        charges_data = data_images['image']
+        charges_pedestals = charges_data[pedestal_mask]
+        # pixel-wise 95% quantile of ped pix charge through the subrun
+        # (#pixels):
+        qt95_pix_charge = np.nanquantile(charges_pedestals, 0.95, axis=0)
+        # ignore pixels with 0 signal:
+        qt95_pix_charge = np.where(qt95_pix_charge > 0, qt95_pix_charge, np.nan)
+        # median of medians across camera:
+        median_qt95_pix_charge = np.nanmedian(qt95_pix_charge)
+        # mean abs deviation of pixel qt95 values:
+        qt95_pix_charge_dev = median_abs_deviation(qt95_pix_charge,
+                                                   nan_policy='omit')
+
+        # Just a cut to remove outliers (pixels):
+        outliers = (np.abs(qt95_pix_charge - median_qt95_pix_charge) /
+                    qt95_pix_charge_dev) > mad_max
+
+        if outliers.sum() > 0:
+            removed_fraction = outliers.sum() / outliers.size
+            log.info(f'    Removed {removed_fraction:.2%} of pixels (outliers) '
+                     f'from pedestal median calculation')
+
+        # Now compute the median (for the whole camera) of the qt95's (for
+        # each pixel) of the charges in pedestal events. Use only reliable
+        # pixels for this, and exclude outliers:
+        n_valid_pixels = np.isfinite(qt95_pix_charge[reliable_pixels]).sum()
+        if n_valid_pixels < min_number_of_valid_pixels:
+            logging.warning(f'    Too few valid pixels ({n_valid_pixels}) for '
+                            f'calculation!')
+            median_ped_qt95_pix_charge.append(np.nan)
+        else:
+            median_ped_qt95_pix_charge.append(np.nanmedian(qt95_pix_charge[
+                                                               reliable_pixels &
+                                                               ~outliers]))
+    # convert to ndarray:
+    median_ped_qt95_pix_charge = np.array(median_ped_qt95_pix_charge)
+    number_of_pedestals = np.array(number_of_pedestals)
+
+    # Now compute the median for all processed subruns, which is more robust
+    # against e.g. subruns affected by car flashes. We exclude subruns
+    # which have less than half of the median statistics per subrun.
+    good_stats = number_of_pedestals > 0.5 * np.median(number_of_pedestals)
+
+    # First check if we have any valid subruns at all:
+    if np.isfinite(median_ped_qt95_pix_charge[good_stats]).sum() ==  0:
+        qped = np.nan
+        qped_dev = np.nan
+        additional_nsb_rate = np.nan
+        log.error(f'No valid computation was possible for run {run_number} with any of the processed subruns!')
+        return qped, additional_nsb_rate, None
+
+    qped = np.nanmedian(median_ped_qt95_pix_charge[good_stats])
+    not_outlier = np.zeros(len(median_ped_qt95_pix_charge), dtype='bool')
+    # Now we also remove outliers (subruns) if any:
+    qped_dev = median_abs_deviation(median_ped_qt95_pix_charge[good_stats])
+    not_outlier = (np.abs(median_ped_qt95_pix_charge - qped) /
+                   qped_dev) < mad_max
+
+    if (~good_stats).sum() > 0:
+        log.info(f'\nNumber of subruns with low statistics: '
+                 f'{(~good_stats).sum()} - removed from pedestal median '
+                 f'calculation')
+    if (~not_outlier).sum() > 0:
+        log.info(f'\nRemoved {(~not_outlier).sum()} outlier subruns '
+                 f'(out of {not_outlier.size}) from pedestal median '
+                 f'calculation')
+
+    # If less than half of the processed files are valid for the final calculation,
+    # we declare it unsuccessful (data probably have problems):
+    if (good_stats & not_outlier).sum() < 0.5 * len(dl1_files):
+        qped = np.nan
+        additional_nsb_rate = np.nan
+        log.error(f'Calculation failed for more than half of the processed subruns of run {run_number}!')
+        return qped, additional_nsb_rate, None
+
+
+    # recompute with good-statistics and well-behaving runs:
+    qped = np.nanmedian(median_ped_qt95_pix_charge[good_stats & not_outlier])
+    log.info(f'\nNumber of subruns used in calculations: '
+             f'{(good_stats & not_outlier).sum()}')
+
+    picture_threshold = pic_th(qped)
+    boundary_threshold = picture_threshold / 2
+
+    # We now create a .json files with recommended image cleaning
+    # settings for lstchain_dl1ab.
+    newconfig = get_standard_config()['tailcuts_clean_with_pedestal_threshold']
+    # casts below are needed, json does not like numpy's int64:
+    newconfig['picture_thresh'] = int(picture_threshold)
+    newconfig['boundary_thresh'] = int(boundary_threshold)
+
+    additional_nsb_rate = get_nsb(qped)
+
+    return qped, additional_nsb_rate, newconfig
+
+
+def pic_th(qt95_ped):
+    """
+    Parameters
+    ----------
+    qt95_ped : float
+        95% quantile of pixel charge in pedestal events (for the standard
+        LocalPeakWindowSearch algo & settings in lstchain)
+
+    Returns
+    -------
+    int
+        recommended picture threshold for image cleaning (from a table)
+
+    """
+    mp_edges = np.array([5.85, 7.25, 8.75, 10.3, 11.67])
+    picture_threshold = np.array([8, 10, 12, 14, 16, 18])
+
+    if qt95_ped >= mp_edges[-1]:
+        return picture_threshold[-1]
+    return picture_threshold[np.where(mp_edges > qt95_ped)[0][0]]
+
+
+def get_nsb(qt95_ped):
+    """
+    Parameters
+    ----------
+    qt95_ped: `float`
+        95% quantile of pixel charge in pedestal events
+
+    Returns
+    -------
+    float
+        (from a parabolic parametrization) the recommended additional NSB
+        (in p.e. / ns) that has to be added to the "dark MC" waveforms in
+        order to match the data for which the 95% quantile of pedestal pixel
+        charge is qt95_ped
+
+    """
+    params = [3.95147396, 0.12642504, 0.01718627]
+    return (params[1] * (qt95_ped - params[0]) +
+            params[2] * (qt95_ped - params[0]) ** 2)

lstchain/scripts/lstchain_dvr_pixselector.py

@@ -27,12 +27,7 @@
 The program creates in the output directory (which is the current by default) 
 a file DVR_settings_LST-1.Run12469.h5 which contains a table "run_summary" 
 which includes the DVR algorithm parameters determined for each processed 
-subrun. It also creates a file with recommended cleaning settings for running 
-DL1ab, based on the NSB level measured in the processed runs. We use
-as picture threshold the closest even number not smaller than the charge 
-"min_charge_for_certain_selection" (averaged for all subruns and rounded) 
-which is the value from which a pixel will be certainly kept by the Data Volume 
-Reduction.
+subrun.
 
 Then we run again the script over all subruns, and using the option to create
 the pixel maks (this can also be done subrun by subrun, to parallelize the
@@ -68,7 +63,6 @@
 from lstchain.paths import parse_dl1_filename
 from lstchain.io.io import dl1_params_lstcam_key, dl1_images_lstcam_key
 from lstchain.io.io import dl1_params_tel_mon_cal_key
-from lstchain.io.config import get_standard_config, dump_config
 
 from ctapipe.io import read_table
 from ctapipe.core import Container, Field
@@ -506,34 +500,6 @@ def main():
                 time.sleep(300)
                 continue
 
-
-    # We now create also .json files with recommended image cleaning
-    # settings for lstchain_dl1ab. We determine the picture threshold 
-    # from the values of min_charge_for_certain_selection:
-
-    if not write_pixel_masks:
-        log.info('Output files:')
-        for file in list_of_output_files:
-            log.info(file)
-            dvrtable = read_table(file, "/run_summary")
-            picture_threshold = get_typical_dvr_min_charge(dvrtable)
-
-            # we round it to an even number of p.e., just to limit the amount 
-            # of different settings in the analysis (i.e. we change 
-            # picture_threshold in steps of 2 p.e.):
-            if picture_threshold % 2 != 0:
-                picture_threshold += 1
-            boundary_threshold = picture_threshold / 2
-            newconfig = get_standard_config()['tailcuts_clean_with_pedestal_threshold']
-            newconfig['picture_thresh'] = picture_threshold
-            newconfig['boundary_thresh'] = boundary_threshold
-            run = int(file.name[file.name.find('Run')+3:-3])
-            json_filename = Path(output_dir, f'dl1ab_Run{run:05d}.json')
-            dump_config({'tailcuts_clean_with_pedestal_threshold': newconfig,
-                         'dynamic_cleaning': get_standard_config()['dynamic_cleaning']},
-                        json_filename, overwrite=True)
-            log.info(json_filename)
-
     log.info('lstchain_dvr_pixselector finished successfully!')