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Owning Palette: Correlation and Spectral Analysis VIs

Installed With: Advanced Signal Processing Toolkit

Computes the single-sided time-cepstrum of an input univariate time series by using a sliding window. You can use the resulting time-cepstrum to detect time-varying periodic components of a time series. Wire data to the Xt input to determine the polymorphic instance to use or manually select the instance.

Example

Use the pull-down menu to select an instance of this VI.

Select an instance TSA Time-Cepstrum (waveform)TSA Time-Cepstrum (array)

TSA Time-Cepstrum (waveform)

	method specifies whether this VI uses the FFT-based or the autoregressive (AR) model-based method to compute the real cepstrum. The default is FFT.
	quefrency offset specifies the offset, in seconds, of the quefrency. This VI returns the real cepstrum at a certain time whose quefrency is larger than the offset value. The default is 0.
	Xt specifies the input univariate time series.
	time-quefrency sampling info specifies information about the density and the size of the time-cepstrum. time steps specifies the sampling period, in number of samples, along the time axis in the joint time-quefrency domain. The default is –1, which specifies that this VI adjusts time steps automatically so that no more than 512 rows exist in the cepstrogram.National Instruments recommends that you set time steps such that the number of rows in cepstrogram does not exceed 512. If you specify a small value for time steps, this VI might return a large cepstrogram, which requires a long computation time and more memory.If you need a small sampling period to observe more details and the signal length is long, divide the signal into smaller segments and compute the cepstrogram for each segment. If the signal is oversampled, you also can downsample the signal. The scale info output contains the actual sampling period, in seconds, along the time axis of the cepstrogram. quefrency bins specifies the number of bins along the quefrency axis of the cepstrogram to sample the time series in the joint time-quefrency domain. quefrency bins must be greater than 0. The scale info output contains the actual sampling period, in seconds, along the quefrency axis of the cepstrogram. The default is 512.
	window info specifies the information about the sliding window that divides the time series Xt into subsequences. type specifies the time-domain window that this VI applies to the time series. 0 None 1 Hanning (default) 2 Hamming 3 Blackman-Harris 4 Exact Blackman 5 Blackman 6 Flat Top 7 4-Term B-Harris 8 7-Term B-Harris 9 Low Sidelobe 10 Gaussian length specifies the length of the window in samples. The default is –1, which indicates that the window length equals the length of the input time series.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	AR setting specifies the settings for the autoregressive (AR) model. This option is valid only when the method is AR Model. AR method specifies the method this VI uses to estimate the autoregressive (AR) model. 0 Forward-Backward (default)—Computes the AR coefficients by minimizing the least-square errors of the forward and backward predictions. 1 Least-Squares—Computes the AR coefficients by minimizing the least-square errors of the forward predictions. 2 Yule-Walker—Computes the AR coefficients by solving the Yule-Walker functions based on the forward predictions. 3 Burg-Lattice—Computes the AR coefficients using the Levinson-Durbin recursion based on the forward and backward predictions. The Levinson-Durbin recursion uses the arithmetic average. 4 Geometric-Lattice—Computes the AR coefficients using the Levinson-Durbin recursion based on the forward and backward predictions. The Levinson-Durbin recursion uses the geometric average. AR order specifies the order of the autoregressive (AR) model. The value of AR order must be greater than 0. The default is 4.
	cepstrogram returns the time-quefrency representation of the time series Xt. Each row corresponds to the real cepstrum at a certain time. The number of rows in cepstrogram equals the signal length divided by time steps.
	scale info returns the time scale and quefrency scale information of the time-quefrency representation, including the time offset, the time interval between every two contiguous rows, the quefrency offset, and the quefrency interval between every two contiguous columns of the cepstrogram.
	overlap returns the overlap, in percentage, of the sliding window this VI applies to the time series.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

TSA Time-Cepstrum (array)

	method specifies whether this VI uses the FFT-based or the autoregressive (AR) model-based method to compute the real cepstrum. The default is FFT.
	quefrency offset specifies the offset, in seconds, of the quefrency. This VI returns the real cepstrum at a certain time whose quefrency is larger than the offset value. The default is 0.
	Xt specifies the input univariate time series.
	time-quefrency sampling info specifies information about the density and the size of the time-cepstrum. time steps specifies the sampling period, in number of samples, along the time axis in the joint time-quefrency domain. The default is –1, which specifies that this VI adjusts time steps automatically so that no more than 512 rows exist in the cepstrogram. National Instruments recommends that you set time steps such that the number of rows in cepstrogram does not exceed 512. If you specify a small value for time steps, this VI might return a large cepstrogram, which requires a long computation time and more memory. If you need a small sampling period to observe more details and the signal length is long, divide the signal into smaller segments and compute the cepstrogram for each segment. If the signal is oversampled, you also can downsample the signal. The scale info output contains the actual sampling period, in seconds, along the time axis of the cepstrogram. quefrency bins specifies the number of bins along the quefrency axis of the cepstrogram to sample the time series in the joint time-quefrency domain. quefrency bins must be greater than 0. The scale info output contains the actual sampling period, in seconds, along the quefrency axis of the cepstrogram. The default is 512.
	window info specifies the information about the sliding window that divides the time series Xt into subsequences. type specifies the time-domain window that this VI applies to the time series. 0 None 1 Hanning (default) 2 Hamming 3 Blackman-Harris 4 Exact Blackman 5 Blackman 6 Flat Top 7 4-Term B-Harris 8 7-Term B-Harris 9 Low Sidelobe 10 Gaussian length specifies the length of the window in samples. The default is –1, which indicates that the window length equals the length of the input time series.
	error in describes error conditions that occur before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node. status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE. code is the error or warning code. The default is 0. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source specifies the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.
	AR setting specifies the settings for the autoregressive (AR) model. This option is valid only when the method is AR Model. AR method specifies the method this VI uses to estimate the autoregressive (AR) model. 0 Forward-Backward (default)—Computes the AR coefficients by minimizing the least-square errors of the forward and backward predictions. 1 Least-Squares—Computes the AR coefficients by minimizing the least-square errors of the forward predictions. 2 Yule-Walker—Computes the AR coefficients by solving the Yule-Walker functions based on the forward predictions. 3 Burg-Lattice—Computes the AR coefficients using the Levinson-Durbin recursion based on the forward and backward predictions. The Levinson-Durbin recursion uses the arithmetic average. 4 Geometric-Lattice—Computes the AR coefficients using the Levinson-Durbin recursion based on the forward and backward predictions. The Levinson-Durbin recursion uses the geometric average. AR order specifies the order of the autoregressive (AR) model. The value of AR order must be greater than 0. The default is 4.
	sampling rate specifies the sampling rate, in hertz, of the input univariate time series Xt. The default is 1.
	cepstrogram returns the time-quefrency representation of the time series Xt. Each row corresponds to the real cepstrum at a certain time. The number of rows in cepstrogram equals the signal length divided by time steps.
	scale info returns the time scale and quefrency scale information of the time-quefrency representation, including the time offset, the time interval between every two contiguous rows, the quefrency offset, and the quefrency interval between every two contiguous columns of the cepstrogram.
	overlap returns the overlap, in percentage, of the sliding window this VI applies to the time series.
	error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error. status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code. source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning.

Example

Refer to the Bearing Time-Cepstrum Analysis VI in the labview\examples\Time Series Analysis\TSAApplications.llb for an example of using the TSA Time-Cepstrum VI.