How to plot envelope of a signal

Hi, I have trouble in plotting a smooth envelope of a signal using the envelope function in Matlab or the hilbert method. The time series of my signal is shown below and I want to obtian the red line to link the peak values.

But using envelope() function or hilbert method, I plot something like

Can anyone help me to solve this questions? Thanks!

I attach my data here.

Answer 1

[Chunru]

load t.mat
load signal.mat
whos

  Name            Size             Bytes  Class     Attributes

  ans             1x35                70  char                
  cmdout          1x33                66  char                
  signal      40001x1             320008  double              
  t           40001x1             320008  double              

plot(t, signal);
hold on
[yupper,ylower] = envelope(signal,1000, 'peak');
plot(t, yupper, 'r--', t, ylower, 'g--')

[Ying Wu]

@Chunru Thanks, that really helps！And I have a follow-up question, since this method seems cannot generate correct envelope for more random waveforms, like this one:

Is there anyway to plot the envelope for this irregular signal?

[Chunru]

There is not a one-for-all method for envelope detection when noise is added. You can try to adjust the window size for your new signal to see if you can obtain a good result.

[Ying Wu]

@Chunru OK, thanks!