1 files changed, 112 insertions, 0 deletions
diff --git a/astro/21cm/get_slice_zfreq.py b/astro/21cm/get_slice_zfreq.py
new file mode 100755
index 0000000..c67d513
--- /dev/null
+++ b/astro/21cm/get_slice_zfreq.py
@@ -0,0 +1,112 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2017 Weitian LI <weitian@aaronly.me>
+# MIT License
+#
+
+"""
+Get the slice of the specified redshift/frequency (21cm signal) from
+the redshift cube (created by `extract_slice.py` and `fitscube.py`)
+using linear interpolation in redshift.
+
+NOTE:
+The cube slices are ordered in increasing redshifts.
+"""
+
+import os
+import sys
+import argparse
+
+import numpy as np
+from astropy.io import fits
+from astropy.wcs import WCS
+
+from z2freq import z2freq, freq2z
+
+
+class FITSCube:
+    def __init__(self, infile):
+        with fits.open(infile) as f:
+            self.data = f[0].data
+            self.header = f[0].header
+        self.wcs = WCS(self.header)
+
+    @property
+    def nslice(self):
+        ns, __, __ = self.data.shape
+        return ns
+
+    @property
+    def redshifts(self):
+        # Z-axis
+        nslice = self.nslice
+        pix = np.zeros(shape=(nslice, 3), dtype=np.int)
+        pix[:, 2] = np.arange(nslice)
+        world = self.wcs.wcs_pix2world(pix, 0)
+        return world[:, 2]
+
+    def get_slice(self, z):
+        redshifts = self.redshifts
+        if z < redshifts.min() or z > redshifts.max():
+            raise ValueError("requested redshift out of range: %.2f" % z)
+        idx2 = (redshifts <= z).sum()
+        idx1 = idx2 - 1
+        z1, slice1 = redshifts[idx1], self.data[idx1, :, :]
+        z2, slice2 = redshifts[idx2], self.data[idx2, :, :]
+        if os.environ.get("DEBUG"):
+            print("DEBUG: redshifts: {0}".format(redshifts), file=sys.stderr)
+            print("DEBUG: z={0}".format(z), file=sys.stderr)
+            print("DEBUG: z1={0}, idx1={1}".format(z1, idx1), file=sys.stderr)
+            print("DEBUG: z2={0}, idx2={1}".format(z2, idx2), file=sys.stderr)
+        return slice1 + (slice2-slice1) * (z-z1) / (z2-z1)
+
+
+def main():
+    outfile_default = "{prefix}_z{z:05.2f}_f{freq:06.2f}.fits"
+
+    parser = argparse.ArgumentParser(
+        description="Get slices at requested redshifts/frequencies")
+    parser.add_argument("-C", "--clobber", dest="clobber",
+                        action="store_true",
+                        help="overwrite existing files")
+    parser.add_argument("-i", "--infile", dest="infile", required=True,
+                        help="input redshift data cube")
+    parser.add_argument("-o", "--outfile", dest="outfile",
+                        default=outfile_default,
+                        help="output FITS image slice (default: %s)" %
+                        outfile_default)
+    parser.add_argument("-p", "--prefix", dest="prefix", required=True,
+                        help="prefix for the output FITS image")
+    exgrp = parser.add_mutually_exclusive_group(required=True)
+    exgrp.add_argument("-z", "--redshifts", dest="redshifts", nargs="+",
+                       help="redshifts where to interpolate slices")
+    exgrp.add_argument("-f", "--freqs", dest="freqs", nargs="+",
+                       help="21cm frequencies [MHz] to interpolate slices")
+    args = parser.parse_args()
+
+    if args.redshifts:
+        redshifts = [float(z) for z in args.redshifts]
+        freqs = z2freq(redshifts, print_=False)
+    else:
+        freqs = [float(f) for f in args.freqs]
+        redshifts = freq2z(freqs, print_=False)
+
+    cube = FITSCube(args.infile)
+    for z, f in zip(redshifts, freqs):
+        outfile = args.outfile.format(prefix=args.prefix, z=z, freq=f)
+        print("z=%05.2f, freq=%06.2f MHz : %s" % (z, f, outfile))
+        zslice = cube.get_slice(z)
+        header = fits.Header()
+        header["BUNIT"] = cube.header.get("BUNIT")
+        header["REDSHIFT"] = (z, "Slice where interpolated")
+        header["FREQ"] = (f, "21cm signal frequency [MHz]")
+        header.add_history(" ".join(sys.argv))
+        hdu = fits.PrimaryHDU(data=zslice, header=header)
+        try:
+            hdu.writeto(outfile, overwrite=args.clobber)
+        except TypeError:
+            hdu.writeto(outfile, clobber=args.clobber)
+
+
+if __name__ == "__main__":
+    main()