{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# How how to use `get_rm_from_altaz`"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can also, for a given time, map the ionospheric rotation measure sky above the observer\n",
    "by giving a set of azimuth and elevation coordinates"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "from __future__ import annotations\n",
    "\n",
    "import astropy.units as u\n",
    "import matplotlib.pyplot as plt\n",
    "import numpy as np\n",
    "from astropy.coordinates import AltAz, EarthLocation\n",
    "from astropy.time import Time\n",
    "from astropy.visualization import quantity_support, time_support\n",
    "from spinifex import get_rm"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "### Required to load local data for example - not needed for normal use\n",
    "from importlib import resources\n",
    "\n",
    "with resources.as_file(resources.files(\"spinifex.data.tests\")) as datapath:\n",
    "    spinifex_data = datapath\n",
    "###"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "times = Time(\"2020-01-08T01:00:00\")\n",
    "# create AltAz grid\n",
    "azangles = np.linspace(0, 360, 30)\n",
    "altangles = np.linspace(10, 90, 8)\n",
    "altazangles = np.meshgrid(azangles, altangles)\n",
    "az = altazangles[0] * u.deg\n",
    "alt = altazangles[1] * u.deg\n",
    "# create Earth Location\n",
    "lon = 6.367 * u.deg\n",
    "lat = 52.833 * u.deg\n",
    "dwingeloo = EarthLocation(lon=lon, lat=lat, height=0 * u.km)\n",
    "# make altaz object, including location and times\n",
    "# get_rm expects a flattened array of coordinates, you can reshape the returned results\n",
    "altaz = AltAz(az=az.flatten(), alt=alt.flatten(), location=dwingeloo, obstime=times)\n",
    "# get rotation measures\n",
    "rm = get_rm.get_rm_from_altaz(\n",
    "    loc=dwingeloo,\n",
    "    altaz=altaz,\n",
    "    # We set these options to use the data packaged with spinifex\n",
    "    # Unsetting them will cause the function to download the data from the internet\n",
    "    prefix=\"cod\",\n",
    "    output_directory=spinifex_data,\n",
    ")\n",
    "rotation_measures = rm.rm.reshape(az.shape)\n",
    "rm_times = rm.times"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "with time_support(), quantity_support():\n",
    "    fig, ax = plt.subplots()\n",
    "    im = ax.pcolormesh(\n",
    "        az,\n",
    "        alt,\n",
    "        rotation_measures,\n",
    "        cmap=plt.cm.RdBu_r,\n",
    "        vmin=-2,\n",
    "        vmax=2,\n",
    "        shading=\"auto\",\n",
    "    )\n",
    "    ax.set_xlabel(\"Azimuth\")\n",
    "    ax.set_ylabel(\"Altitude\")\n",
    "\n",
    "    fig.colorbar(im, label=\"Rotation Measure [rad/m$^2$]\")\n",
    "    fig, ax = plt.subplots(subplot_kw={\"projection\": \"polar\"})\n",
    "    im = ax.pcolormesh(\n",
    "        az.to(u.rad).value,\n",
    "        90 - alt.to(u.deg).value,\n",
    "        rotation_measures,\n",
    "        cmap=plt.cm.RdBu_r,\n",
    "        vmin=-2,\n",
    "        vmax=2,\n",
    "        shading=\"auto\",\n",
    "    )\n",
    "    fig.colorbar(im, label=\"Rotation Measure [rad/m$^2$]\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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