CS_VO_Tables.ipynb

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 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Creating a VO Table from a CSV file"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "\n",
    "There are several ways of doing this, and there are a few object layers here, which can be confusing:\n",
    "- Standard [astropy Table](https://docs.astropy.org/en/stable/table/) objects\n",
    "- [Votable Table](https://docs.astropy.org/en/stable/api/astropy.io.votable.tree.Table.html#astropy.io.votable.tree.Table) objects\n",
    "- [Votable VOTableFile](https://docs.astropy.org/en/stable/api/astropy.io.votable.tree.VOTableFile.html#astropy.io.votable.tree.VOTableFile) objects (may contain multiple votable Tables)\n",
    "\n",
    "Although some things can be done with generic astropy Tables, other VO operations can only be done with VO Tables or VOTableFile objects.  \n",
    "\n",
    "This is easiest to see with an example.  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import io, numpy\n",
    "\n",
    "from astropy import table as aptable\n",
    "from astropy.io import votable as apvot"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Create a table with only two columns starting from an astropy Table"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "myaptable=aptable.Table(\n",
    "    numpy.array([\n",
    "            [19.0186,       46.7304],\n",
    "            [20.2887,       40.4703],\n",
    "            [125.886,       21.3377],\n",
    "            [136.002,       21.9679],\n",
    "            [141.057,       40.6372],\n",
    "            [146.700,       22.0116],\n",
    "            [148.785,       14.2922],\n",
    "            [149.751,       17.8168],\n",
    "            [175.039,       15.3270],\n",
    "            [191.542,       30.7317],\n",
    "            [194.913,       28.8959],\n",
    "            [199.026,       41.5011],\n",
    "            [206.577,       43.8511],\n",
    "            [209.963,       38.1821],\n",
    "            [213.556,       15.6214],\n",
    "            [219.967,       42.7421],\n",
    "            [226.693,       12.8502],\n",
    "            [237.489,       20.8057],\n",
    "            [241.519,       20.8014],\n",
    "            [317.088,       18.2002],\n",
    "            [329.235,       6.64845],\n",
    "            [333.830,       37.3012] ]), \n",
    "    names=[\"RA\",\"DEC\"])\n",
    "\n",
    "print(type(myaptable))\n",
    "print(myaptable)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "#### Then convert this to a VOTableFile object which contains a nested set of *resources* and *tables* (in this case, only one of each)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "myvotablefile = apvot.from_table(myaptable)\n",
    "print(type(myvotablefile))\n",
    "\n",
    "for r in myvotablefile.resources:\n",
    "    mytable=r\n",
    "    for t in r.tables:\n",
    "        print(t)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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