corrected formula in GP marginal notebook (#64)

Author: patel-zeel

examples/gaussian_processes/GP-Marginal.ipynb

@@ -41,7 +41,7 @@
     "  -\\frac{1}{2} (\\mathbf{y} - \\mathbf{m}_x)^{T} \n",
     "               (\\mathbf{K}_{xx} + \\boldsymbol\\Sigma)^{-1} \n",
     "               (\\mathbf{y} - \\mathbf{m}_x)\n",
-    "  - \\frac{1}{2}|\\mathbf{K}_{xx} + \\boldsymbol\\Sigma|\n",
+    "  - \\frac{1}{2}\\log(\\mathbf{K}_{xx} + \\boldsymbol\\Sigma)\n",
     "  - \\frac{n}{2}\\log (2 \\pi)\n",
     "$$\n",
     "\n",
@@ -732,9 +732,9 @@
  "metadata": {
   "anaconda-cloud": {},
   "kernelspec": {
-   "display_name": "pymc-dev",
+   "display_name": "Python 3",
    "language": "python",
-   "name": "pymc-dev"
+   "name": "python3"
   },
   "language_info": {
    "codemirror_mode": {
@@ -746,7 +746,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.7"
+   "version": "3.8.5"
   }
  },
  "nbformat": 4,