code: def average_sweep(self,T1=0,T2=None,sweeps=None,stdErr=False):
          
          T1=T1*self.rate
          if T2 is None:
              T2 = self.sweepSize-1
          else:
              T2 = T2*self.rate
          if sweeps is None:
              sweeps = range(self.sweeps)
          Ys=np.empty((len(sweeps),(T2-T1)))
          for i in range(len(sweeps)):
              self.setSweep(sweeps[i])
              Ys[i]=self.dataY[T1:T2]
          Av = np.average(Ys,0)
          Es = np.std(Ys,0)
          Xs = self.dataX[T1:T2]
          if stdErr: #otherwise return stdev
              Es = Es/np.sqrt(len(sweeps))
          return Xs,Av,Es
docs: given an array of sweeps, return X,Y,Err average.
          This returns *SWEEPS* of data, not just 1 data point.