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From: Gunjan on 28 Jun 2010 13:04
Hi,

am trying to use the continuous wavelet transform code and having some difficulties. My goal is to perform cwt within the frequency range of 30-120 Hz and also I am trying to use at least 10 scales per octave. I am confused about the parameters "dj" and "s0" in the wavetest code that came with the package. If anyone can please help me with this, it will be really great. Thanks.

-Gunjan.
From: Wayne King on 28 Jun 2010 13:40
"Gunjan " <geophy_02(a)hotmail.com> wrote in message <i0akm7$1hd$1(a)fred.mathworks.com>...
> Hi,
>
> am trying to use the continuous wavelet transform code and having some difficulties. My goal is to perform cwt within the frequency range of 30-120 Hz and also I am trying to use at least 10 scales per octave. I am confused about the parameters "dj" and "s0" in the wavetest code that came with the package. If anyone can please help me with this, it will be really great. Thanks.
>
> -Gunjan.

Hi Gunjan, dj is the spacing between scales. It corresponds to 1:dj:N scales input in the MATLAB cwt. s0 is the smallest scale wavelet.

Wayne
From: Gunjan on 28 Jun 2010 14:41
"Wayne King" <wmkingty(a)gmail.com> wrote in message <i0amqa$n0q$1(a)fred.mathworks.com>...
> "Gunjan " <geophy_02(a)hotmail.com> wrote in message <i0akm7$1hd$1(a)fred.mathworks.com>...
> > Hi,
> >
> > am trying to use the continuous wavelet transform code and having some difficulties. My goal is to perform cwt within the frequency range of 30-120 Hz and also I am trying to use at least 10 scales per octave. I am confused about the parameters "dj" and "s0" in the wavetest code that came with the package. If anyone can please help me with this, it will be really great. Thanks.
> >
> > -Gunjan.
>
> Hi Gunjan, dj is the spacing between scales. It corresponds to 1:dj:N scales input in the MATLAB cwt. s0 is the smallest scale wavelet.
>
> Wayne

Hi Wayne,

So if I need to start at a frequency 30Hz, should I be using 1/30 as s0? and to go up to 120Hz, j1 would be 3/dj where dj=0.1 for 10 scales per octave. Thanks.

-Gunjan.
From: Wayne King on 29 Jun 2010 07:00
"Gunjan " <geophy_02(a)hotmail.com> wrote in message <i0aqc1$kk9$1(a)fred.mathworks.com>...
> "Wayne King" <wmkingty(a)gmail.com> wrote in message <i0amqa$n0q$1(a)fred.mathworks.com>...
> > "Gunjan " <geophy_02(a)hotmail.com> wrote in message <i0akm7$1hd$1(a)fred.mathworks.com>...
> > > Hi,
> > >
> > > am trying to use the continuous wavelet transform code and having some difficulties. My goal is to perform cwt within the frequency range of 30-120 Hz and also I am trying to use at least 10 scales per octave. I am confused about the parameters "dj" and "s0" in the wavetest code that came with the package. If anyone can please help me with this, it will be really great. Thanks.
> > >
> > > -Gunjan.
> >
> > Hi Gunjan, dj is the spacing between scales. It corresponds to 1:dj:N scales input in the MATLAB cwt. s0 is the smallest scale wavelet.
> >
> > Wayne
>
> Hi Wayne,
>
> So if I need to start at a frequency 30Hz, should I be using 1/30 as s0? and to go up to 120Hz, j1 would be 3/dj where dj=0.1 for 10 scales per octave. Thanks.
>
> -Gunjan.

Hi Gunjan, s0 is the smallest scale (highest frequency), you're thinking of it in terms of the lowest frequency, which would correspond to the longest scale.

So if you only want up to approximately 120 Hz, you base s0 on that. Express that in terms of your sampling interval.

Hope that helps,
Wayne
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