## General options

Purpose

Description

Tips

Macro Synopsis

Modules

Related Functions

References

### Purpose

Signal processing default settings

### Description

"General options" changes the default settings for the FFT algorithm, the windowing type and the interpolation type. Note the global relevance of these settings. Since interpolation is used implicitly every time two signals of unequal sampling period (scale) and / or x-axis-offset (shift) are combined, these settings have global effects on most of the functions. **Warning:** *In order to avoid confusion, make sure that the x-axis units of the input signals to be combined are equal since there is no automatic unit conversion.*
Changing the FFT type and windowing type will affect most frequency-domain (spectral) functions.
Parameters for "General options" are

- Type (
`type`) of interpolation:
- "Linear" (0) : Linear interpolation between consecutive samples
- "Lagrange" (1) : Performs a polynomial interpolation of
the (odd) order given in the second parameter (see below).
- "Resample" (2) : Re-samples the signal to a new size using
low-pass filtering in the time domain according to the sampling theorem.
**Warning:** *Due to the filtering algorithm used, shift errors can occur if the x-axis offsets of the two signals are not identical.*
- "Spline" (3) : Perfoms a cubic spline interpolation.

- (odd) Lagrange interpolation order (
`order`) ranging from
1 to 7. An interpolation of order 1 corresponds to linear
interpolation. For interpolation types other than Lagrange the
order is ignored.

- The type of Fast Fourier transform (
`ffttype`) is one of
- "Mixed Radix" (0)
- "Cooley-Tukey" (1)
- "Radix 2" (2)

- Windowing type
`wintype`:
- "Bartlett'' (0)
- "Blackman'' (1)
- "Boxcar'' (2)
- "Hamming'' (3)
- "Hanning'' (4)
- "Kaiser'' (5)
- "Parzen'' (6)
- "Potter'' (7)
- "Welch'' (8)

### Tips

In general, smooth functions are best approximated by higher
order polynomials, whereas for functions with sharp corners or rapidly
changing higher derivatives, the choice of lower-order or even
linear approximation gives more accurate results.

### Macro Synopsis

`BasicOptions(type, order);`

option type;

int order;

SpectralOptions(ffttype, wintype);

option fftype,wintype;
Note: The `order` parameter for BasicOptions must be given even if it is not used.

### Modules

Student, Professional

### Related Functions

Resample, Fourier transform, Apply window.

### References

Press et al. [16], Crochiere/Rabiner [17], Oppenheim/Schafer [3]