vis.frequency.compute_halfwidth

  COMPUTE_HALFWIDTH - find where signal reaches maximum, 1/2 on left side, 1/2 on right side

      [LOW,MAX,HIGH] = COMPUTE_HALFWIDTH( X, Y )

      returns MAX, where x position where function attains its maximum value
      LOW < MAX,  where function attains half its maximum
      HIGH > MAX, where function attains half its maximum
      returns NAN for LOW or/and HIGH, when function does not come below the point

      See also: COMPUTE_HALFWIDTH_INTERP