Do not modify argument x of `plot_distr_funct`

Do not modify dummy argument x of `plot_distr_funct`.

Inst_eddies/Analysis/distribution_function.py

@@ -9,14 +9,14 @@ from os import path
 def plot_distr_funct(x, label = None, ax = None):
     """Sort and plot distribution function. x should be a Numpy array."""
     
-    x.sort()
+    x_sorted = np.sort(x)
     nx = np.size(x)
     
     if nx != 0:
         if ax is None: fig, ax = plt.subplots()
-        ax.plot(x, (1 + np.arange(nx)) / nx, label = label)
-        print("minimum value:", x[0])
-        print("maximum value:", x[-1])
+        ax.plot(x_sorted, (1 + np.arange(nx)) / nx, label = label)
+        print("minimum value:", x_sorted[0])
+        print("maximum value:", x_sorted[- 1])
         
     print("number of values:", nx, "\n")