diff options
Diffstat (limited to 'pyspike/PieceWiseLinFunc.py')
-rw-r--r-- | pyspike/PieceWiseLinFunc.py | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/pyspike/PieceWiseLinFunc.py b/pyspike/PieceWiseLinFunc.py index f2442be..c0dd475 100644 --- a/pyspike/PieceWiseLinFunc.py +++ b/pyspike/PieceWiseLinFunc.py @@ -29,6 +29,64 @@ class PieceWiseLinFunc: self.y1 = np.array(y1) self.y2 = np.array(y2) + def __call__(self, t): + """ Returns the function value for the given time t. If t is a list of + times, the corresponding list of values is returned. + + :param: time t, or list of times + :returns: function value(s) at that time(s). + """ + def intermediate_value(x0, x1, y0, y1, x): + """ computes the intermediate value of a linear function """ + return y0 + (y1-y0)*(x-x0)/(x1-x0) + + assert np.all(t >= self.x[0]) and np.all(t <= self.x[-1]), \ + "Invalid time: " + str(t) + + ind = np.searchsorted(self.x, t, side='right') + + if isinstance(t, collections.Sequence): + # t is a sequence of values + # correct the cases t == x[0], t == x[-1] + ind[ind == 0] = 1 + ind[ind == len(self.x)] = len(self.x)-1 + value = intermediate_value(self.x[ind-1], + self.x[ind], + self.y1[ind-1], + self.y2[ind-1], + t) + # correct the values at exact spike times: there the value should + # be the at half of the step + # obtain the 'left' side indices for t + ind_l = np.searchsorted(self.x, t, side='left') + # if left and right side indices differ, the time t has to appear + # in self.x + ind_at_spike = np.logical_and(np.logical_and(ind != ind_l, + ind > 1), + ind < len(self.x)) + # get the corresponding indices for the resulting value array + val_ind = np.arange(len(ind))[ind_at_spike] + # and for the values in self.x, y1, y2 + xy_ind = ind[ind_at_spike] + # the values are defined as the average of the left and right limit + value[val_ind] = 0.5 * (self.y1[xy_ind-1] + self.y2[xy_ind-2]) + return value + else: # t is a single value + # specific check for interval edges + if t == self.x[0]: + return self.y1[0] + if t == self.x[-1]: + return self.y2[-1] + # check if we are on any other exact spike time + if sum(self.x == t) > 0: + # use the middle of the left and right Spike value + return 0.5 * (self.y1[ind-1] + self.y2[ind-2]) + return intermediate_value(self.x[ind-1], + self.x[ind], + self.y1[ind-1], + self.y2[ind-1], + t) + def copy(self): """ Returns a copy of itself |