Proper nside change in tutorial_datasets

tutorials/tutorial_datasets.ipynb

@@ -72,13 +72,14 @@
     "from imagine.observables import FaradayDepthHEALPixDataset\n",
     "import numpy as np\n",
     "from astropy import units as u\n",
+    "import healpy as hp\n",
     "\n",
     "# Adjusts the data to the right format\n",
     "fd_raw = raw_dataset[3].data.astype(np.float)\n",
     "sigma_fd_raw = raw_dataset[4].data.astype(np.float)\n",
-    "# Makes it small, to save memory\n",
-    "fd_raw = fd_raw[::256]\n",
-    "sigma_fd_raw = sigma_fd_raw[::256]\n",
+    "# Makes it smaller, to save memory\n",
+    "fd_raw = hp.pixelfunc.ud_grade(fd_raw, 4)\n",
+    "sigma_fd_raw = hp.pixelfunc.ud_grade(sigma_fd_raw, 4)\n",
     "# We need to include units the data\n",
     "# (this avoids later errors and inconsistencies)\n",
     "fd_raw *= u.rad/u.m/u.m\n",
@@ -108,28 +109,23 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "import requests, io\n",
-    "import numpy as np\n",
-    "from astropy.io import fits\n",
-    "from astropy import units as u\n",
     "from imagine.observables import FaradayDepthHEALPixDataset\n",
     "\n",
     "class FaradayDepthOppermann2012(FaradayDepthHEALPixDataset):\n",
-    "    def __init__(self, skip=None):\n",
+    "    def __init__(self, Nside=None):\n",
     "        # Fetches and reads the \n",
     "        download = requests.get('https://wwwmpa.mpa-garching.mpg.de/ift/faraday/2012/faraday.fits')\n",
     "        raw_dataset = fits.open(io.BytesIO(download.content))\n",
     "        # Adjusts the data to the right format\n",
     "        fd_raw = raw_dataset[3].data.astype(np.float)\n",
     "        sigma_fd_raw = raw_dataset[4].data.astype(np.float)\n",
+    "        # Reduces the resolution\n",
+    "        if Nside is not None:\n",
+    "            fd_raw = hp.pixelfunc.ud_grade(fd_raw, Nside)\n",
+    "            sigma_fd_raw = hp.pixelfunc.ud_grade(sigma_fd_raw, Nside)\n",
     "        # Includes units in the data\n",
     "        fd_raw *= u.rad/u.m/u.m\n",
     "        sigma_fd_raw *= u.rad/u.m/u.m\n",
-    "        \n",
-    "        # If requested, makes it small, to save memory in this example\n",
-    "        if skip is not None:\n",
-    "            fd_raw = fd_raw[::skip]\n",
-    "            sigma_fd_raw = sigma_fd_raw[::skip]\n",
     "        # Loads into the Dataset\n",
     "        super().__init__(data=fd_raw, error=sigma_fd_raw)"
    ]
@@ -147,7 +143,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "dset = FaradayDepthOppermann2012(skip=256)"
+    "dset = FaradayDepthOppermann2012(Nside=4)"
    ]
   },
   {
@@ -199,7 +195,7 @@
      "data": {
       "text/html": [
        "<i>Table length=3</i>\n",
-       "<table id=\"table139726377436496\" class=\"table-striped table-bordered table-condensed\">\n",
+       "<table id=\"table140085692999504\" class=\"table-striped table-bordered table-condensed\">\n",
        "<thead><tr><th>RAJ2000</th><th>DEJ2000</th><th>GLON</th><th>GLAT</th><th>RM</th><th>e_RM</th><th>PI</th><th>I</th><th>S5.2</th><th>f_S5.2</th><th>NVSS</th></tr></thead>\n",
        "<thead><tr><th>&quot;h:m:s&quot;</th><th>&quot;d:m:s&quot;</th><th>deg</th><th>deg</th><th>rad / m2</th><th>rad / m2</th><th>mJy</th><th>mJy</th><th></th><th></th><th></th></tr></thead>\n",
        "<thead><tr><th>bytes11</th><th>bytes11</th><th>float32</th><th>float32</th><th>int16</th><th>int16</th><th>float32</th><th>float64</th><th>bytes3</th><th>bytes1</th><th>bytes4</th></tr></thead>\n",
@@ -322,11 +318,11 @@
      "output_type": "stream",
      "text": [
       "Measurement keys:\n",
-      "\t ('fd', None, 8, None)\n",
+      "\t ('fd', None, 4, None)\n",
       "\t ('fd', None, 'tab', None)\n",
       "\n",
       "Covariance keys:\n",
-      "\t ('fd', None, 8, None)\n",
+      "\t ('fd', None, 4, None)\n",
       "\t ('fd', None, 'tab', None)\n"
      ]
     }
@@ -352,8 +348,15 @@
     "\n",
     "* If data is independent from frequency, data-freq is set `None`, otherwise it is the frequency in GHz.\n",
     "* The third value in the key-tuple is the HEALPix Nside (for maps) or the string 'tab' for tabular data. \n",
-    "* Finally, the last value, `ext` can be 'I','Q','U','PI','PA', None or other customized tags depending on the nature of the observable.\n",
-    "            \n",
+    "* Finally, the last value, `ext` can be 'I','Q','U','PI','PA', None or other customized tags depending on the nature of the observable."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Manually including data\n",
+    "\n",
     "An alternative way to include data into an Observables dictionary is explicitly choosing the key and adjusting the data shape. One can see how this is handled by the Dataset object in the following cell"
    ]
   },
@@ -366,14 +369,16 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "The key used in the \"name\" arg was: ('fd', None, 8, None)\n",
-      "The shape of data used in the \"new\" arg was: (1, 768)\n"
+      "The key used in the \"name\" arg was: ('fd', None, 4, None)\n",
+      "The shape of data used in the \"new\" arg was: (1, 192)\n"
      ]
     }
    ],
    "source": [
     "# This is how HEALPix data can be included without the mediation of Datasets:\n",
     "mea.append(name=dset.key, data=dset.data)\n",
+    "# The units of covariance matrices have to be provided separately\n",
+    "# (as sparse matrices to not support them)\n",
     "cov.append(name=dset.key, data=dset.cov)\n",
     "# This is what Dataset is doing:\n",
     "print('The key used in the \"name\" arg was:', dset.key)\n",