Re: sine wave equations

[Paul Roberts]

Most likely just an aliasing problem. Make sure that you have a high
enough sampling frequency in x. For example, lets say that x
represents space. The spatial frequency of your sine wave seems to be
1/lambda. To sample the function properly, your delta_x should be at
least as small as lambda/2. So you would use:

delta_x = lambda/2;
x = x_min:delta_x:x_max;

If you wanted to oversample, you could use a smaller delta_x

Paul

On 12/2/06, Doug Stewart <address@hidden> wrote:
> What do you mean when you say corrupted sin waves?   Do you want more
> samples per sin wave?
>
> What values are you using for
> lambda =?
> x=?
>
> Doug Stewart
>
> MICHAEL FORREST wrote:
> > Dear all,
> >
> > I am using NEURON simulation package, a tool for simulating Neurons. In the
> > simulation I am currently building I am using sine wave equations. And the
> > sine wave plots look somewhat corrupted. Not all the waves are of the same
> > shape etc. Now, there must be loads of people on this list that know these
> > sine equations backwards. So, I write to kindly ask if my equations are OK.
> > I write because my NEURON simulation is not working as desired - and a fault
> > in the sine wave equations is one candidate. I have already done a little
> > check myself by using an online plotting applet to see what their plot looks
> > like. ANd it looks fine! So I write to this list as an extra check.
> >
> > 2 one dimensional sine wave equations 180 degrees out of phase (with an
> > offset, D, for each, that ensures the centre is non-zero. So that we dont
> > ever have negative values).
> >
> > y(x) = A*sin(((2*PI*x)/lambda)-0) + D
> > where A = D
> >
> > y(x) = A*sin(((2*PI*x)/lambda)-PI) + D
> > where A = D
> >
> > Now, I have tried these alternative equations as well. These form corrupted
> > sine waves as well:
> >
> > y(x) = A*sin(((360*x)/lambda)-0) + D
> > where A = D
> >
> > y(x) = A*sin(((360*x)/lambda)-180) + D
> > where A = D
> >
> > For anyone that wants to go deeper into my problem (though this would
> > require some neuroscience knowledge) there is a running thread on it at this
> > forum (NEURON forum hosted at Yale):
> >
> > https://www.neuron.yale.edu/phpBB2/viewtopic.php?p=2312#2312
> >
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