code: def lp_tri(f, fb):
      
  
      x = np.zeros(len(f))
      for k in range(len(f)):
          if abs(f[k]) <= fb:
              x[k] = 1 - abs(f[k])/float(fb)
      return x
docs: Triangle spectral shape function used by :func:`lp_samp`.
  
      Parameters
      ----------
      f : ndarray containing frequency samples
      fb : the bandwidth as a float constant
      
      Returns
      -------
      x : ndarray of spectrum samples for a single triangle shape
  
      Notes
      -----
      This is a support function for the lowpass spectrum plotting function
      :func:`lp_samp`.
  
      Examples
      --------
      >>> x = lp_tri(f, fb)