added frd to matlab compat file, fixed FRD construction from 1d data

repagh · repagh · commit 80edad6ee635 · 2013-05-23T15:40:01.000Z
diff --git a/src/frdata.py b/src/frdata.py
@@ -107,7 +107,7 @@ class FRD(Lti):
     def __init__(self, *args, **kwargs):
         """Construct a transfer function.
         
-        The default constructor is FRD(w, d), where w is an iterable of 
+        The default constructor is FRD(d, w), where w is an iterable of 
         frequency points, and d is the matching frequency data. 
         
         If d is a single list, 1d array, or tuple, a SISO system description 
@@ -142,8 +142,8 @@ def __init__(self, *args, **kwargs):
                 # The user provided a response and a freq vector
                 self.fresp = array(args[0], dtype=complex)
                 if len(self.fresp.shape) == 1:
-                    self.fresp.reshape(1, 1, len(args[0]))
-                self.omega = array(args[1])
+                    self.fresp = self.fresp.reshape(1, 1, len(args[0]))
+                self.omega = array(args[1], dtype=float)
                 if len(self.fresp.shape) != 3 or \
                         self.fresp.shape[-1] != self.omega.shape[-1] or \
                         len(self.omega.shape) != 1:
@@ -189,9 +189,9 @@ def __str__(self):
                 if mimo:
                     outstr.append("Input %i to output %i:" % (i + 1, j + 1))
                 outstr.append('Freq [rad/s]  Response   ')
-                outstr.append('------------  ------------------------')
+                outstr.append('------------  ---------------------')
                 outstr.extend(
-                    [ '%12.3f  %10.4g + %10.4g' % (w, m, p)
+                    [ '%12.3f  %10.4g%+10.4gj' % (w, m, p)
                       for m, p, w in zip(real(self.fresp[j,i,:]), imag(self.fresp[j,i,:]), wt) ])
 
 
diff --git a/src/matlab.py b/src/matlab.py
@@ -89,6 +89,7 @@
 from control.statesp import StateSpace, _rss_generate, _convertToStateSpace
 from control.xferfcn import TransferFunction, _convertToTransferFunction
 from control.lti import Lti #base class of StateSpace, TransferFunction
+from control.frdata import FRD
 from control.dtime import sample_system
 from control.exception import ControlArgument
 
@@ -125,7 +126,7 @@
 \*  :func:`ss`                  create state-space (SS) models
 \   dss                         create descriptor state-space models
 \   delayss                     create state-space models with delayed terms
-\   frd                         create frequency response data (FRD) models
+\*  :func:`frd`                 create frequency response data (FRD) models
 \   lti/exp                     create pure continuous-time delays (TF and
                                 ZPK only)
 \   filt                        specify digital filters
@@ -156,7 +157,7 @@
 \*  :func:`tf`                  conversion to transfer function
 \   zpk                         conversion to zero/pole/gain
 \*  :func:`ss`                  conversion to state space
-\   frd                         conversion to frequency data
+\*  :func:`frd`                 conversion to frequency data
 \   c2d                         continuous to discrete conversion
 \   d2c                         discrete to continuous conversion
 \   d2d                         resample discrete-time model
@@ -569,6 +570,42 @@ def tf(*args):
     else:
         raise ValueError("Needs 1 or 2 arguments; received %i." % len(args))
 
+def frd(*args):
+    '''
+    Construct a Frequency Response Data model, or convert a system
+
+    frd models store the (measured) frequency response of a system.
+
+    This function can be called in different ways:
+
+    ``frd(response, freqs)``
+        Create an frd model with the given response data, in the form of
+        complex response vector, at matching frequency freqs [in rad/s]
+
+    ``frd(sys, freqs)``
+        Convert an Lti system into an frd model with data at frequencies
+        freqs. 
+
+    Parameters
+    ----------
+    response: array_like, or list
+        complex vector with the system response
+    freq: array_lik or lis
+        vector with frequencies
+    sys: Lti (StateSpace or TransferFunction)
+        A linear system
+
+    Returns
+    -------
+    sys: FRD
+        New frequency response system
+
+    See Also
+    --------
+    ss, tf
+    '''
+    return FRD(*args)
+
 
 def ss2tf(*args):
     """
diff --git a/tests/matlab_test.py b/tests/matlab_test.py
@@ -13,6 +13,7 @@
 import numpy as np
 import scipy as sp
 from control.matlab import *
+from control.frdata import FRD
 
 class TestMatlab(unittest.TestCase):
     def setUp(self):
@@ -408,7 +409,14 @@ def testConnect(self):
         np.testing.assert_array_almost_equal(
             sysc.D, np.mat('0; 0'))
                                  
-
+    def testFRD(self):
+        h = tf([1], [1, 2, 2])
+        omega = np.logspace(-1, 2, 10)
+        frd1 = frd(h, omega)
+        assert isinstance(frd1, FRD)
+        frd2 = frd(frd1.fresp[0,0,:], omega)
+        assert isinstance(frd2, FRD)
+       
 
 #! TODO: not yet implemented
 #    def testMIMOtfdata(self):
