lesson 4: unpack state, and use raw strings in figures

Author: labarba

notebooks_en/4_Birdseye_Vibrations.ipynb

@@ -300,7 +300,7 @@
     "pyplot.xlabel('Time [s]')\n",
     "pyplot.ylabel('Position, $x$ [m]')\n",
     "pyplot.title('Damped spring-mass system with Euler-Cromer method.\\n')\n",
-    "pyplot.figtext(0.1,-0.1,'$m={:.1f}$, $k={:.1f}$, $b={:.1f}$'.format(m,k,b));"
+    "pyplot.figtext(0.1,-0.1, r'$m={:.1f}$, $k={:.1f}$, $b={:.1f}$'.format(m,k,b));"
    ]
   },
   {
@@ -406,8 +406,8 @@
     "    -------\n",
     "    derivs: derivatives of the state vector\n",
     "    '''\n",
-    "      \n",
-    "    derivs = numpy.array([state[1], 1/m*(F(time)-k*state[0]-b*state[1])])\n",
+    "    x, v = state  \n",
+    "    derivs = numpy.array([v, 1/m*(F(time)-k*x -b*v)])\n",
     "    return derivs"
    ]
   },
@@ -457,7 +457,7 @@
     "pyplot.xlabel('Time [s]')\n",
     "pyplot.ylabel('Position, $x$ [m]')\n",
     "pyplot.title('Driven spring-mass system with Euler-Cromer method.\\n')\n",
-    "pyplot.figtext(0.1,-0.1,'$m={:.1f}$, $k={:.1f}$, $b={:.1f}$, $A={:.1f}$, $\\omega={:.1f}$'.format(m,k,b,A,ω));"
+    "pyplot.figtext(0.1,-0.1,r'$m={:.1f}$, $k={:.1f}$, $b={:.1f}$, $A={:.1f}$, $\\omega={:.1f}$'.format(m,k,b,A,ω));"
    ]
   },
   {
@@ -534,7 +534,7 @@
     "pyplot.xlabel('Time [s]')\n",
     "pyplot.ylabel('Position, $x$ [m]')\n",
     "pyplot.title('Driven spring-mass system with Euler-Cromer method.\\n')\n",
-    "pyplot.figtext(0.1,-0.1,'$m={:.1f}$, $k={:.1f}$, $b={:.1f}$, $A={:.1f}$, $\\omega={:.1f}$'.format(m,k,b,A,ω));"
+    "pyplot.figtext(0.1,-0.1, r'$m={:.1f}$, $k={:.1f}$, $b={:.1f}$, $A={:.1f}$, $\\omega={:.1f}$'.format(m,k,b,A,ω));"
    ]
   },
   {