Update dynamical_system.py

dynamical_system.py

@@ -11,4 +11,12 @@ def invasion_fitness2(z, zm, pars):
 
 def pop_dynamics2(t, n, pars):
     alpha, beta, z = pars
-    return n * (z - z**beta - alpha * n)
+    return n * (z - z**beta - alpha * n)
+
+def invasion_fitness3(z, zm, pars):
+    z0, k = pars
+    r = np.exp(-((z - z0) ** 2) / 2)
+    n_res = r
+    rm = np.exp(-((zm - z0) ** 2) / 2)
+    am = np.exp(-((zm - z) ** 2) / k)
+    return rm - am * n_res