code: def _fwhm_side_lineal(uu, vv):
      '''Compute r12 using linear interpolation.'''
      res1, = np.nonzero(vv < 0)
      if len(res1) == 0:
          return 0, 1  # error, no negative value
      else:
          # first value
          i2 = res1[0]
          i1 = i2 - 1
          dx = uu[i2] - uu[i1]
          dy = vv[i2] - vv[i1]
          r12 = uu[i1] - vv[i1] * dx / dy
          return r12, f _fwhm_side_lineal(uu, vv):
      '''Compute r12 using linear interpolation.'''
      res1, = np.nonzero(vv < 0)
      if len(res1) == 0:
          return 0, 1  # error, no negative value
      else:
          # first value
          i2 = res1[0]
          i1 = i2 - 1
          dx = uu[i2] - uu[i1]
          dy = vv[i2] - vv[i1]
          r12 = uu[i1] - vv[i1] * dx / dy
          return r12, 0
docs: Compute r12 using linear interpolation.