Geopsy: Decimate time - Revision history

Clotaire Michel at 13:45, 12 March 2010

2010-03-12T13:45:55Z

Pierre-Yves Bard at 08:24, 12 March 2010

2010-03-12T08:24:11Z

Pierre-Yves Bard at 08:20, 12 March 2010

2010-03-12T08:20:57Z

Pierre-Yves Bard at 08:14, 12 March 2010

2010-03-12T08:14:49Z

Clotaire Michel at 16:52, 10 March 2010

2010-03-10T16:52:44Z

Clotaire Michel at 11:56, 10 March 2010

2010-03-10T11:56:54Z

Clotaire Michel at 11:00, 10 March 2010

2010-03-10T11:00:57Z

Clotaire Michel: New page: '''Decimate time''', reached from the Waveform menu, decreases the sampling frequency of signals in the active signal viewer. By clickin...

2010-03-10T10:47:17Z

New page: '''Decimate time''', reached from the Waveform menu, decreases the sampling frequency of signals in the active signal viewer. By clickin...

New page

'''Decimate time''', reached from the [[Geopsy: Waveform Menu|Waveform menu]], decreases the sampling frequency of signals in the active [[Geopsy: Signal Viewer|signal viewer]]. By clicking on ''Decimate time'', a pop-up window appears requesting the decimation factor, i.e. the ratio between current sampling frequency and desired sampling frequency.

''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia: Nyquiest|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Over sample]] tool. Moreover, this factor should be an '''integer value'''. In order to decimate by a non-integer rational value \<math>frac{p}{q}</math>, first Over sample by ''q'' and Decimate by ''p''.

The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every two samples.

''Decimate time'' modifies the [[Geopsy: Temporary Signal|temporary signals]] in the active viewer.

See also:
[[Wikipedia:decimate|Decimation (Wikipedia)]]

@@ Line 7: / Line 7: @@
 The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every '''<math>p</math>''' samples (for a decimation factor equal to '''<math>p</math>'''.
-''Decimate time'' modifies the [[Geopsy: Temporary Signal|temporary signals]] in the active viewer.
+''Decimate time'' creates new [[Geopsy: Temporary Signal|temporary signals]] in the active viewer.
 See also:
 *[[Wikipedia:Decimation_(signal_processing)|Decimation (Wikipedia)]]
 *[[Wikipedia:Nyquist_frequency|Nyquist frequency (Wikipedia)]]

@@ Line 5: / Line 5: @@
 ''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Oversample]] tool. Moreover, this factor should be an '''integer value <math>p</math>'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first ''Over sample'' by <math>q</math> and ''Decimate'' by <math>p</math>.
-The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every two samples.
+The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every '''<math>p</math>''' samples (for a decimation factor equal to '''<math>p</math>'''.
 ''Decimate time'' modifies the [[Geopsy: Temporary Signal|temporary signals]] in the active viewer.

@@ Line 3: / Line 3: @@
 '''Decimate time''', reached from the [[Geopsy: Waveform Menu|Waveform menu]], decreases the sampling frequency of signals in the active [[Geopsy: Signal Viewer|signal viewer]]. By clicking on ''Decimate time'', a pop-up window appears requesting the decimation factor, i.e. the ratio between current sampling frequency and desired sampling frequency.
-''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Oversample]] tool. Moreover, this factor should be an '''integer value'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first ''Over sample'' by <math>q</math> and ''Decimate'' by <math>p</math>.
+''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Oversample]] tool. Moreover, this factor should be an '''integer value <math>p</math>'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first ''Over sample'' by <math>q</math> and ''Decimate'' by <math>p</math>.
 The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every two samples.

@@ Line 3: / Line 3: @@
 '''Decimate time''', reached from the [[Geopsy: Waveform Menu|Waveform menu]], decreases the sampling frequency of signals in the active [[Geopsy: Signal Viewer|signal viewer]]. By clicking on ''Decimate time'', a pop-up window appears requesting the decimation factor, i.e. the ratio between current sampling frequency and desired sampling frequency.
-''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Over sample]] tool. Moreover, this factor should be an '''integer value'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first ''Over sample'' by <math>q</math> and ''Decimate'' by <math>p</math>.
+''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Oversample]] tool. Moreover, this factor should be an '''integer value'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first ''Over sample'' by <math>q</math> and ''Decimate'' by <math>p</math>.
 The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every two samples.

@@ Line 1: / Line 1: @@
 '''Decimate time''', reached from the [[Geopsy: Waveform Menu|Waveform menu]], decreases the sampling frequency of signals in the active [[Geopsy: Signal Viewer|signal viewer]]. By clicking on ''Decimate time'', a pop-up window appears requesting the decimation factor, i.e. the ratio between current sampling frequency and desired sampling frequency.
-''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Over sample]] tool. Moreover, this factor should be an '''integer value'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first Over sample by <math>q</math> and Decimate by <math>p</math>.
+''Decimate time'' is used to decrease the size of manipulated signals, when their sampling frequency is larger than 2 times the largest frequency of interest [[Wikipedia:Nyquist_frequency|(Nyquist frequency)]]. The decimation factor should be greater than 1, values lower than one correspond to oversampling that can be achieved using the [[Geopsy: Over sample|Over sample]] tool. Moreover, this factor should be an '''integer value'''. In order to decimate by a non-integer rational value <math>\frac{p}{q}</math>, first ''Over sample'' by <math>q</math> and ''Decimate'' by <math>p</math>.
 The decimation algorithm first applies a low-pass anti-aliasing filter in the frequency domain, in that case a [[Geopsy: Filter#Cosine Taper|tapered cosine filter]] of 20% width, with the cut-off frequency equal to half of the desired sampling frequency. Then, in the time domain, one sample is kept every two samples.