Computes the continuous wavelet transform (CWT) of the 1D input signal with real-valued wavelets. Wire data to the signal input to determine the polymorphic instance to use or manually select the instance.


icon

Inputs/Outputs

  • ci32.png time steps —

    time steps specifies the number of samples to translate, or shift, the wavelet in the continuous wavelet transform (CWT). The default is -1, which specifies that this VI adjusts time steps automatically so that no more than 512 coefficients exist at each scale.

  • c1ddbl.png signal —

    signal specifies the input signal.

  • ci32.png scales —

    scales specifies the number of scales of the dilated wavelet.

  • cu16.png wavelet —

    wavelet specifies the wavelet type to use to compute the continuous wavelet coefficients. The default is db02. The options include the following types: Mexican Hat, Meyer, Morlet, orthogonal (Haar, Daubechies (dbxx), Coiflets (coifx), Symmlets (symx)) and biorthogonal (Biorthogonal (biorx_x), including FBI (bior4_4 (FBI))), where x indicates the order of the wavelet.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • c1ddbl.png user defined scales —

    user defined scales specifies the scales to use to compute CWT coef. The scale must be positive and no greater than the length of signal. If you specify a value for user defined scales, this VI ignores the settings in the scales input.

  • ccclst.png user defined wavelet —

    user defined wavelet specifies the mother wavelet function to use to compute the continuous wavelet transform (CWT). If you specify a value for user defined wavelet, this VI ignores the settings in the wavelet input. You can use the Wavelet Design Express VI to design the wavelet.

  • cdbl.png t0 —

    t0 specifies the initial time of the mother wavelet function.

  • cdbl.png dt —

    dt specifies the time interval of the mother wavelet function in samples.

  • c1ddbl.png mother wavelet —

    mother wavelet specifies the mother wavelet function.

  • i2ddbl.png CWT coef —

    CWT coef returns the results of the continuous wavelet transform (CWT).

  • ifxdt.png scale info —

    scale info returns the time information and the scale (frequency) information, which this VI uses in the scalogram plot.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

    • WA Continuous Wavelet Transform Details

    The following equation defines the CWT:

    where s(t) is the signal, is the mother wavelet function, and a and are the scale and shift of the wavelet, respectively. a can be any positive real value. Use user defined scales to specify the scales. If you do not specify values for user defined scales, this VI selects the scale, a, as 1, 2, 3,…, scales. This VI selects the shift, , as 0, dt, 2dt, 3dt,…, Ndt, where dt is time steps, and N is approximately equal to the signal length divided by time steps. Refer to A Wavelet Tour of Signal Processing for more information about the CWT.

    Examples

    Refer to the Breakdown Point Detection VI in the labview\examples\Wavelet Analysis\WAApplications directory for an example of using the WA Continuous Wavelet Transform VI.