Scipy Numpy Lectures - Adding Finite & Infinite

Finite and Infinite
Test element-wise for finiteness and infinity

Author: TarrySingh

numpy/SciPy Numpy Lecture 2 - Numerical operations on arrays.ipynb

@@ -1411,9 +1411,9 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "#### Had we done np.any() \n",
+    "#### If we would have done `np.any()`...\n",
     "\n",
-    "What would the answer be then?"
+    "What would then the answer be then?"
    ]
   },
   {
@@ -1436,14 +1436,180 @@
     "((a <= b) & (b <= c)).any()"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "### Finite and Infinite\n",
+    "\n",
+    "Test element-wise for finiteness and infinity"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 79,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 79,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "np.isfinite(1) # 1 is finite"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 88,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 88,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "np.isfinite(np.exp(100))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 89,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/tarrysingh/anaconda/lib/python3.6/site-packages/ipykernel_launcher.py:1: RuntimeWarning: overflow encountered in exp\n",
+      "  \"\"\"Entry point for launching an IPython kernel.\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "False"
+      ]
+     },
+     "execution_count": 89,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "np.isfinite(np.exp(1000))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 85,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/tarrysingh/anaconda/lib/python3.6/site-packages/ipykernel_launcher.py:1: RuntimeWarning: overflow encountered in exp\n",
+      "  \"\"\"Entry point for launching an IPython kernel.\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "inf"
+      ]
+     },
+     "execution_count": 85,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "np.exp(1000)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "#### Above is a limitation of my computer...\n",
+    "\n",
+    "The answer should actually be true...\n",
+    "\n",
+    "...**but** if we do `np.isinf()'"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 90,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "/Users/tarrysingh/anaconda/lib/python3.6/site-packages/ipykernel_launcher.py:1: RuntimeWarning: overflow encountered in exp\n",
+      "  \"\"\"Entry point for launching an IPython kernel.\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 90,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "np.isinf(np.exp(1000))"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 91,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "False"
+      ]
+     },
+     "execution_count": 91,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "np.isfinite(np.inf) # Kind of obvious as infinity is definitely NOT finite"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
    "metadata": {
     "collapsed": true
    },
    "outputs": [],
-   "source": []
+   "source": [
+    "np.isfinite(np.log(-1.), 1., np.lo)"
+   ]
   }
  ],
  "metadata": {