[mDistribution,___] = envelope()
  [mDistribution,___] = envelope('Fourier Space')
 
  depending on which dimension you use (t,x,y,r) use:
  [mDistribution, vT] = envelope()
  [mDistribution, vR] = envelope()
  [mDistribution, vX] = envelope()
  [mDistribution, vT, vX] = envelope()
  [mDistribution, vT, vR] = envelope()
  [mDistribution, vX, vY] = envelope()
  [mDistribution, vT, vX, vY] = envelope()
  mDistribution are  A(t), A(r), A(x), A(t, x), A(t, r), A(x, y),
  A(t, x, y) respectively. The result is given in [V/m].
 
  [mDistribution, vAF] = envelope('Fourier Space')
  [mDistribution, vKR] = envelope('Fourier Space')
  [mDistribution, vKX] = envelope('Fourier Space')
  [mDistribution, vAF, vKX] = envelope('Fourier Space')
  [mDistribution, vAF, vKR] = envelope('Fourier Space')
  [mDistribution, vKX, vKY] = envelope('Fourier Space')
  [mDistribution, vAF, vKX, vKY] = envelope('Fourier Space')
  mDistribution are A(\omega), A(k_r), A(k_x), A(\omega, k_x),
  A(\omega, k_r), A(k_x, k_y) A(\omega, k_x, k_y), respectively.
  The result is given in arbitrary units.