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    Finds the location, amplitude, and second derivative of peaks or valleys in the input signal.

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    X

    The array of input values that represents the signal to be analyzed. The data can be a single array or consecutive blocks of data. Consecutive blocks of data are useful for large data arrays or for real time processing. Notice that in real time processing, peaks/valleys are not detected until approximately width/2 data points past the peak or valley.

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    threshold

    A double that instructs this node to ignore peaks and valleys that are too small. This node ignores peaks if the fitted amplitude is less than threshold. This node ignores valleys if the fitted trough is greater than threshold.

    Default: 0

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    width

    The number of consecutive data points to use in the quadratic least squares fit. width is coerced to a value greater than or equal to 3. The value should be no more than about 1/2 of the half-width of the peaks/valleys and can be much smaller (but >2) for noise-free data. Large widths can reduce the apparent amplitude of peaks and shift the apparent location. For noisy data, this modification is unimportant since the noise obscures the actual peak. Ideally, width should be as small as possible but must be balanced against the possibility of false peak detection due to noise.

    Default: 3

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    peaks/valleys

    An enum that determines whether the node looks for peaks or valleys in the input signal.

    Peaks

    Looks for peaks in the input signal.

    Valleys

    Looks for valleys in the input signal.

    Default: Peaks

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    initialize (T)

    A Boolean that determines whether to process the first block of data.

    TRUE Processes only the first block of data.
    FALSE Processes consecutive blocks of data.

    This node requires some internal setup at the beginning for proper operation. If you only want to process one block of data, set initialize to TRUE. If you want to process consecutive blocks of data, set initialize to TRUE for the first block and FALSE for all other blocks of data.

    Default: TRUE

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    end of data (T)

    A Boolean that determines whether to process only one block of data.

    TRUE Processes only one block of data.
    FALSE Processes consecutive blocks of data.

    After processing the last block of data, this node manages internal data. If you only want to process one block of data, set end of data to be TRUE. If you want to process consecutive blocks of data, set end of data to FALSE for all but the last block of data.

    Default: TRUE

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    # found

    The number of peaks/valleys found in the current block of data. # found is the size of the arrays Locations, Amplitudes, and 2nd Derivatives.

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    Locations

    The index locations of all peaks or valleys detected in the current block of data.

    Because the peak detection algorithm uses a quadratic fit to find the peaks, it actually interpolates between the data points. Therefore, the indexes are not integers. In other words, the peaks found are not necessarily actual points in the input data but may be at fractions of an index and at amplitudes not found in the input array. To view the locations in terms of time, use the following equation:

    Time Locations[i] = t0 + dt*Locations[i]

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    Amplitudes

    The amplitudes of peaks or valleys found in the current block of data.

    Note  

    The Locations and Amplitudes might deviate from actual peaks or valleys for noisy signals with large dynamic ranges.

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    2nd Derivatives

    The measurements of the second derivative of the amplitude at each of the peaks or valleys found in the current block of data. 2nd Derivatives gives an approximate measure of the sharpness of each peak or valley. If you are detecting peaks, these values are all negative. If you are detecting valleys, the values are all positive.

    Note  

    It is assumed that dt, the time difference between samples, is equal to 1.

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    error

    A value that represents any error or warning that occurs when this node executes.