Re: problem with plot / hold

[Matthias Brennwald]

> Message: 4
> Date: Thu, 25 May 2006 13:30:53 +0200
> From: Javier Arantegui <address@hidden>
> Subject: Re: problem with plot / hold
> To: address@hidden
> Message-ID: <address@hidden>
> Content-Type: text/plain;  charset="iso-8859-1"
>
> Hi,
>
> I haven't used Matlab in my life, so I don't know if this solution  
> will work
> in Matlab.
>
> El Jueves, 25 de Mayo de 2006 12:16, Matthias Brennwald escribi?:
> > In Matlab, these commands to exactly what I want. In Octave, however,
> > the second plot contains all three data sets instead of only the
> > third set.
>
> The solution is very easy:
>
> subplot(2,1,1);     % open up the first plot
> plot(rand(1,10));   % plot the first data set to the first plot
> hold on             % hold the plot
> plot(rand(1,10));   % plot the second data to the first plot
>
> hold off
>
> subplot(2,1,2);     % open up the second plot
> plot(rand(1,10));   % plot the third data set to the second plot
>
> Javier

Ok, that does the trick. However, I'm not yet happy... I should have  
modelled my example closer to my real-world problem.

What I'm trying to do is the following: I analyze a loudspeaker  
system using either Octave or Matlab and a custom sound in/out system.
In a first step, I measure some data and plot this data in different  
ways on different plots (impulse response in one plot and step  
response in the other plot). After looking at these plots, I decide  
to change the speaker in some way, re-measure the data, and plot the  
results for comparison with the first measurement. In other words:

* I measure the impulse response and calculate the step response from  
the impulse response.
* I plot the impulse response to the first plot, the step response to  
the second plot.
* After looking at these plots, I change the loudspeaker system and  
re-analyses it.
* Then, I want to plot the impulse response of the new measurement to  
the first plot, keeping the the impulse response from the first  
measurement for reference.
* Also, I want to plot the step response of the new measurement to  
the second plot, keeping the the step response from the first  
measurement for reference.

This can be illustrated by the following code (which does exactly  
what I want with Matlab, but not with Octave):

t = [0:100]; h1 = sin(t).*exp(-t/5);    % invent some fake  
measurement data of the first measurement ( impulse response h1(t) )
subplot(2,1,1);                         % open up the plot for the  
impulse response
plot(t,h1);                             % plot the impulse response  
from the first measurement
hold on                                 % hold the plot to allow  
comparison with future measurement(s)
subplot(2,1,2);                         % open up the plot for the  
step response
plot(t,cumsum(h1));                     % plot the step response from  
the first measurement
hold on                                 % hold the plot to allow  
comparison with future measurement(s)

h2 = sin(1.2*t).*exp(-t/7);             % invent some fake  
measurement data of the second measurement ( impulse response h(t) )
subplot(2,1,1);                         % go to the plot for the  
impulse response
plot(t,h2);                             % plot the impulse response  
from the second measurement
subplot(2,1,2);                         % go to the plot for the step  
response
plot(t,cumsum(h2));                     % plot the step response from  
the second measurement

Again: In Matlab, these commands do exactly what I want. In Octave,  
however, the second plot contains more plots than intended. Where's  
my mistake?

Is there a way to make my code 'universal' such that it runs as  
intended both with Matlab and Octave?

Matthias