Envelope(s​ignal,np,'​peak') error in Matlab R2015b

I am trying to use the envelope function on MATLAB R2015b and I get the following error:

"Error using envelope

Too many input arguments.

Error in envelope_trial (line 7)

[up,low ]= envelope(x,30,'peak');"

x is simply a vector computed in this way:

"t = 0:1e-4:1; x = [1+cos(2*pi*50*t)].*cos(2*pi*1000*t);"

The MATLAB R2016b online documentation explains how to use this function and I am following striclty the instructions (https://es.mathworks.com/help/signal/ref/envelope.html#buv7i12-1).

What is the problem?

Answer 1

[Honglei Chen]

Do you have another envelope function on your path? What does

which envelope

return? If it does not point to the one under toolbox/signal/signal, then another function with the same name is shadowing it.

HTH

Answer 2

[Image Analyst]

This works for me

t = 0:1e-4:1; 
x = [1+cos(2*pi*50*t)].*cos(2*pi*1000*t);
[up,low ]= envelope(x,30,'peak');
plot(t, x, 'b*-');
hold on;
plot(t, up, 'r*-');
plot(t, low, 'g*-');

Do this and tell me what you see:

>> which -all envelope

Do you see only this:

C:\Program Files\MATLAB\R2016b\toolbox\signal\signal\envelope.m