updated nb

Author: shenmingfu

DP1/100_How_to_Use_RSP_Tools/103_Image_access_and_display/103_8_Image_display_with_matplotlib.ipynb

@@ -804,7 +804,7 @@
    "id": "232f4189-d6f3-49f2-b5ce-4c65a0360de4",
    "metadata": {},
    "source": [
-    "Retrieve the `patch` and the objects' x and y coordinates."
+    "Retrieve the `patch`, the objects' x and y coordinates, and the r-band Point Spread Function (PSF) flux (with uncertainty)."
    ]
   },
   {
@@ -815,7 +815,8 @@
    "outputs": [],
    "source": [
     "use_columns = ['objectId', 'patch',\n",
-    "               'r_centroid_x', 'r_centroid_y']\n",
+    "               'r_centroid_x', 'r_centroid_y',\n",
+    "               'r_psfFlux', 'r_psfFluxErr']\n",
     "objects = butler.get('object', tract=dataId.get('tract'),\n",
     "                     parameters={'columns': use_columns})"
    ]
@@ -839,6 +840,27 @@
     "print(\"Number of objects: \", len(tx))"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "ac155358-63e0-424a-aa3e-e2bb674356b7",
+   "metadata": {},
+   "source": [
+    "Since there are many objects, filter objects by their Signal-to-Noise ratio (S/N) to make the following scatter plot more clear. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "ca27a145-8b32-4647-bd94-3f13a4766fc3",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "sel = objects['r_psfFlux'] / objects['r_psfFluxErr'] > 300\n",
+    "objects = objects[sel]\n",
+    "tx = np.where(objects['patch'] == dataId.get('patch'))[0]\n",
+    "print(\"Number of objects: \", len(tx))"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "8cd049b7-b478-4cea-943b-a7e9dc75dc90",
@@ -863,7 +885,7 @@
     "    for i in tx:\n",
     "        afw_display.dot('o', objects[i]['r_centroid_x'],\n",
     "                        objects[i]['r_centroid_y'],\n",
-    "                        size=20, ctype='orange')\n",
+    "                        size=30, ctype='orange')\n",
     "plt.show()\n",
     "remove_figure(fig)"
    ]
@@ -904,14 +926,34 @@
     "dataId = visit_image_refs[0].dataId\n",
     "\n",
     "use_columns = ['sourceId', 'visit',\n",
-    "               'x', 'y']\n",
+    "               'x', 'y',\n",
+    "               'psfFlux', 'psfFluxErr']\n",
     "\n",
     "sources = butler.get('source', dataId=dataId,\n",
     "                     parameters={'columns': use_columns})\n",
     "\n",
     "print(\"Number of sources: \", len(sources))"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "0f14f134-308c-4ead-b759-70d610d03718",
+   "metadata": {},
+   "source": [
+    "Filter the sources by S/N."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c34db8eb-09fd-487f-b6f7-a7320851e2df",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "sel = sources['psfFlux'] / sources['psfFluxErr'] > 300\n",
+    "sources = sources[sel]"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "a94cacd5-1b60-4943-9c88-381c87f14490",
@@ -936,7 +978,7 @@
     "    for i in sources:\n",
     "        afw_display.dot('o', i['x'],\n",
     "                        i['y'],\n",
-    "                        size=3, ctype='orange')\n",
+    "                        size=30, ctype='orange')\n",
     "plt.show()\n",
     "remove_figure(fig)"
    ]