First version of the pdf_analysis module

Maybe we should change the name.

pcigale/analysis_modules/pdf_analysis/utils.py

+# -*- coding: utf-8 -*-
+# Copyright (C) 2013 Centre de données Astrophysiques de Marseille
+# Copyright (C) 2014 Yannick Roehlly <yannick@iaora.eu>
+# Licensed under the CeCILL-v2 licence - see Licence_CeCILL_V2-en.txt
+# Author: Yannick Roehlly
+
+import numpy as np
+from copy import deepcopy
+from ...sed.cosmology import cosmology
+from ...creation_modules import get_module as get_creation_module
+
+
+def gen_compute_fluxes_at_redshift(sed, filters, redshifting_module,
+                                   igm_module):
+    """"Generate function to compute the fluxes of a SED at a given redshift
+
+    Given a SED, a list of filters and a redshift module name, this generator
+    returns a function computing the fluxes of the SED in all the filters at
+    a given redshift.  If the SED is older than the Universe at the given
+    redshift, the fluxes returned by this function will be all -99.
+
+    If the redshift module name is None, the SED is not redshifted by the
+    returned function. This means that it will always return the same fluxes,
+    whatever its redshift parameter. This can be used for computing
+    photometric redshifts.
+
+    Parameters
+    ----------
+    sed : pcigale.sed
+        The pcigale SED object.
+    filters : list of pcigale.data.filters
+        List of pcigale filters objects.
+    redshifting_module : picgale.creation_modules.Module
+        A pcigale SED creation module to redshift the SED. It must accept a
+        redshift parameter (or be None).
+    igm_module : picgale.creation_modules.Module
+        A pcigale SED creation module to add the IGM attenuation to the SED.
+        Is not used if the redshifting module is None.
+
+    Return
+    ------
+    gen_fluxes : function
+        Function computing the fluxes of the SED in all filters at a given
+        redshift.
+
+    """
+    # The returned function is memoized.
+    cache = {}
+
+    def gen_fluxes(redshift):
+        """Compute the flux of the SED in various filters.
+
+        Parameters
+        ----------
+        redshift : float
+
+        Returns
+        -------
+        array fo floats
+
+        """
+
+        # If the function is generated without a redshift module, it always
+        # computes the fluxes at the SED redshift (the SED may be already
+        # redshifted).
+        if not redshifting_module:
+            redshift = sed.redshift
+
+        if redshift not in cache:
+            # Age of the Universe at redshift.
+            # astropy 0.3 cosmology functions return quantities
+            try:
+                age_at_redshift = cosmology.age(redshift).value * 1000
+            except AttributeError:
+                age_at_redshift = cosmology.age(redshift) * 1000
+
+            if sed.info["age"] > age_at_redshift:
+                cache[redshift] = -99 * np.ones(len(filters))
+            else:
+
+                if redshifting_module:
+                    red_sed = deepcopy(sed)
+                    redshifting_module.parameters["redshift"] = redshift
+                    redshifting_module.process(red_sed)
+                    if igm_module:
+                        igm_module.process(red_sed)
+                else:
+                    red_sed = sed
+
+                cache[redshift] = np.array(
+                    [red_sed.compute_fnu(filt_.trans_table,
+                                         filt_.effective_wavelength)
+                     for filt_ in filters])
+
+        return cache[redshift]
+
+    return gen_fluxes