https://pfspipe.ipmu.jp/jira This file is an XML representation of an issue en-us 8.3.4 803005 13-09-2019 https://pfspipe.ipmu.jp/jira/browse/PIPE2D-342 DRP 2-D Pipeline <p>Define a class for Line Spread Function information. This should ideally be a subset of the <tt>Psf</tt> class and thus have similar methods, such that it and the <tt>Psf</tt> class can be used in generic code.</p> <p>How the LSF is stored internally in given <tt>Lsf</tt> instance needs to be determined, as an analytical form may be useful in addition to a numerical form (an array of amplitudes versus x-position).</p> PIPE2D-342

Define {{Lsf}} class

Task Normal Done Done price hassan Thu, 7 Feb 2019 18:34:41 +0000 Mon, 4 Jan 2021 20:23:07 +0000 Wed, 25 Mar 2020 22:34:15 +0000 6.0 0 6 <p>I've defined <tt>Lsf</tt> as an abstract base class, and provided a couple of example subclasses.</p> <p>Glancing through the pull request it wasn't obvious that this class duck-types as a <tt>Psf</tt>. Does it?  Actually, I don't quite see why it can't be the same class (with a 1xN image) and some pybind11 magic to always do the .array.</p> <p>Why can't a Kernel be an <tt>afw.Image</tt>?  And I'm a bit worried about the name clashing with an afw.math.Kernel in people's minds (not the code).</p> <p>Does this class support undersampled data?  This isn't critical yet, but it may be (well, should be if Jim builds a good spectrograph).</p> <p>Why provide the computeStdev method?  It's a naïve implementation – what is it for?  Theoretically the stdev of a perfect diffraction grating is infinite (as it is for a perfect diffraction-limited PSF) so this isn't just a concern about noise.</p> <p>I can think of other methods (e.g. offset Lsf by delta) but I don't think we should try to invent them now.</p> <p>While the <tt>Lsf</tt> is related to an LSST <tt>Psf</tt> (in terms of history), it does not duck type as one. Is that a requirement? If so, can you give examples where you would make use of that?</p> <p><tt>computeStdev</tt> is the one-dimensional equivalent of <a href="http://doxygen.lsst.codes/stack/doxygen/x_masterDoxyDoc/classlsst_1_1afw_1_1detection_1_1_psf.html#a8067ecbd3d52dffe8ff822500257d4fe" class="external-link" rel="nofollow"><tt>Psf::computeShape</tt></a>: it's the width of a line. Would a different name (<tt>computeFwhm</tt>?) help?</p> <p>As currently implemented, the base class convenience implementation of <tt>computeArray</tt> does not support undersampled data (it acts like LSST's <tt>Psf</tt>, just in 1D). To handle that, we'll need to make a subclass that does something clever, or use a functional form like the <tt>GaussianLsf</tt>.</p> <p>The LSF needs to duck-type as a PSF, both to make it easier to use and (more importantly) to allow code that models spectra to work on 1-D and 2-D spectra.</p> <p> </p> <p>I've made the <tt>Lsf</tt> duck type as an LSST <tt>Psf</tt>. It will not work for C++ code (e.g., <tt>exposure.setPsf(lsf)</tt> won't work) because it's defined in python, but it should work in <tt>Task</tt> codes where the <tt>Psf</tt> is provided separately.</p> <p>Please have another look.</p> <p>Addressed <a href="https://pfspipe.ipmu.jp/jira/secure/ViewProfile.jspa?name=rhl" class="user-hover" rel="rhl">rhl</a>'s comments and merged to master.</p> Blocks PIPE2D-349 PIPE2D-333 Relates PIPE2D-346 DAMD-9 PIPE2D-343 Development Epic Link PIPE2D-352 Rank 0|02qprv:c8 Reviewers hassan Sprint 2DDRP-2019 C 2DDRP-2019 D 2DDRP-2019 E 2DDRP-2019 G 2DDRP-2019 H 2DDRP-2019 I 2DDRP-2019 J 2DDRP-2021 A Story Points 4.0