[python-control-discuss] consistency of parameters to phase_plot()

[Scott C. L. <sli...@ca...>]

The docstring for phase_plot() (in src/phaseplot.py) concerning the parameter "T" is

  Length of time to run simulations that generate streamlines.                            
  If a single number, the same simulation time is used for all                            
  initial conditions.  Otherwise, should be a list of length                              
  len(X0) that gives the simulation time for each initial                                 
  condition.  Default value = 50.

It appears to me that the second possibility of "list of length len(X0)" is not actually implemented.  Instead, if T is an array, then it is used in the call to odeint() directly.  I propose adding the claimed functionality and further, in the case that T is a list, allowing any element to be an array itself.  A patch achieving this is below.  Existing code that uses phase_plot() would be unaffected by this change assuming that T is never given as a list.

Index: src/phaseplot.py
===================================================================
--- src/phaseplot.py	(revision 202)
+++ src/phaseplot.py	(working copy)
@@ -176,6 +176,8 @@
     dx = np.empty((nr, Narrows, 2))
   
     # See if we were passed a simulation time
+    if isinstance(T, list) and len(T) != nr:
+        raise TypeError("Insufficient number of simulation times given for initial conditions.")
     if (T == None):
         T = 50
 
@@ -197,6 +199,10 @@
 
     # Generate the streamlines for each initial condition
     for i in range(nr):
+        if isinstance(T, list):
+            TSPAN = T[i]
+            if (isinstance(TSPAN, (int, float))):
+                TSPAN = np.linspace(0, TSPAN, 100);
         state = odeint(odefun, X0[i], TSPAN, args=parms);
         time = TSPAN
         mpl.hold(True);