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From: sharmin shamsalsadati on 9 Jul 2010 11:08
Hi

I want to plot a wavelet (Ricker wavelet) in the time domain using this formula:
s(t)=(1-2*pi^2*f^2*(t-tc))*exp(-pi^2*f^2*(t-tc)^2);
(t=-1:0.01:1;)
and also add a 45 degree phase shift in to that. I multipled s(t) by exp(i*pi/4) to do so, but it finds error using that .It doesn't consider the phase shift(it says that the imaginary part is ignored). I am not sure how to the phase shift in to the wavelet in time-domain using Matlab.

I will appreciate your helps and suggestions.
From: someone on 9 Jul 2010 12:48
"sharmin shamsalsadati" <sharmin_shamsalsadati(a)yahoo.com> wrote in message <i17e0k$o3e$1(a)fred.mathworks.com>...
> Hi
>
> I want to plot a wavelet (Ricker wavelet) in the time domain using this formula:
> s(t)=(1-2*pi^2*f^2*(t-tc))*exp(-pi^2*f^2*(t-tc)^2);
> (t=-1:0.01:1;)
> and also add a 45 degree phase shift in to that. I multipled s(t) by exp(i*pi/4) to do so, but it finds error using that .It doesn't consider the phase shift(it says that the imaginary part is ignored). I am not sure how to the phase shift in to the wavelet in time-domain using Matlab.
>
> I will appreciate your helps and suggestions.

% What does your code look like and what exact error message do you get?

% This works for me:

t=-1:0.01:1;
f = 1000; % dummy data
tc = 0.1; % dummy data

s = (1-2*pi^2*f^2*(t-tc)).*exp(-pi^2*f^2*(t-tc).^2);
s1 = s.*exp(i*pi/4); % 45 deg phase shifted?

% Note the use of the dot operator (element-by-element).
From: sharmin shamsalsadati on 9 Jul 2010 14:53
"someone" <someone(a)somewhere.net> wrote in message <i17js3$nr5$1(a)fred.mathworks.com>...
> "sharmin shamsalsadati" <sharmin_shamsalsadati(a)yahoo.com> wrote in message <i17e0k$o3e$1(a)fred.mathworks.com>...
> > Hi
> >
> > I want to plot a wavelet (Ricker wavelet) in the time domain using this formula:
> > s(t)=(1-2*pi^2*f^2*(t-tc))*exp(-pi^2*f^2*(t-tc)^2);
> > (t=-1:0.01:1;)
> > and also add a 45 degree phase shift in to that. I multipled s(t) by exp(i*pi/4) to do so, but it finds error using that .It doesn't consider the phase shift(it says that the imaginary part is ignored). I am not sure how to the phase shift in to the wavelet in time-domain using Matlab.
> >
> > I will appreciate your helps and suggestions.
>
> % What does your code look like and what exact error message do you get?
>
> % This works for me:
>
> t=-1:0.01:1;
> f = 1000; % dummy data
> tc = 0.1; % dummy data
>
> s = (1-2*pi^2*f^2*(t-tc)).*exp(-pi^2*f^2*(t-tc).^2);
> s1 = s.*exp(i*pi/4); % 45 deg phase shifted?
>
> % Note the use of the dot operator (element-by-element).
This is my code:
f=50;
t=-1:0.01:1;
s=(((1-2*pi^2*f^2*(t-tc).^2).*exp(-pi^2*f^2*(t-tc).^2)));
s1=s.*exp(i*pi/4);
plot(s1,t)
It shows a warning message: "Imaginary parts of complex X and/or Y arguments ignored" and the plot it gives me doesn't have the phase shift applied in to that.

Thank you
From: someone on 9 Jul 2010 15:10
"sharmin shamsalsadati" <sharmin_shamsalsadati(a)yahoo.com> wrote in message <i17r6f$h6h$1(a)fred.mathworks.com>...
> "someone" <someone(a)somewhere.net> wrote in message <i17js3$nr5$1(a)fred.mathworks.com>...
> > "sharmin shamsalsadati" <sharmin_shamsalsadati(a)yahoo.com> wrote in message <i17e0k$o3e$1(a)fred.mathworks.com>...
> > > Hi
> > >
> > > I want to plot a wavelet (Ricker wavelet) in the time domain using this formula:
> > > s(t)=(1-2*pi^2*f^2*(t-tc))*exp(-pi^2*f^2*(t-tc)^2);
> > > (t=-1:0.01:1;)
> > > and also add a 45 degree phase shift in to that. I multipled s(t) by exp(i*pi/4) to do so, but it finds error using that .It doesn't consider the phase shift(it says that the imaginary part is ignored). I am not sure how to the phase shift in to the wavelet in time-domain using Matlab.
> > >
> > > I will appreciate your helps and suggestions.
> >
> > % What does your code look like and what exact error message do you get?
> >
> > % This works for me:
> >
> > t=-1:0.01:1;
> > f = 1000; % dummy data
> > tc = 0.1; % dummy data
> >
> > s = (1-2*pi^2*f^2*(t-tc)).*exp(-pi^2*f^2*(t-tc).^2);
> > s1 = s.*exp(i*pi/4); % 45 deg phase shifted?
> >
> > % Note the use of the dot operator (element-by-element).
> This is my code:
> f=50;
> t=-1:0.01:1;
> s=(((1-2*pi^2*f^2*(t-tc).^2).*exp(-pi^2*f^2*(t-tc).^2)));
> s1=s.*exp(i*pi/4);
> plot(s1,t)
> It shows a warning message: "Imaginary parts of complex X and/or Y arguments ignored" and the plot it gives me doesn't have the phase shift applied in to that.
>
> Thank you

% So, your problem is with the plot command.

doc plot

% As the help says (first paragraph in description):

plot(Y) plots the columns of Y versus
their index if Y is a real number. If Y is
complex, plot(Y) is equivalent to plot(real(Y),imag(Y)).
In all other uses of plot, the imaginary component is ignored.

% Think about what you are doing.
% Hint: perhaps you need to use the abs function.
From: Walter Roberson on 9 Jul 2010 15:17
sharmin shamsalsadati wrote:

> This is my code:
> f=50;
> t=-1:0.01:1;
> s=(((1-2*pi^2*f^2*(t-tc).^2).*exp(-pi^2*f^2*(t-tc).^2)));
> s1=s.*exp(i*pi/4); plot(s1,t)
> It shows a warning message: "Imaginary parts of complex X and/or Y
> arguments ignored" and the plot it gives me doesn't have the phase shift
> applied in to that.

plot(real(s1),t,'r',imag(s1),t,'g',abs(s1),t,'b');
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