## Basic Options

Purpose

Description

Tips

Macro Synopsis

Modules

Related Functions

References

### Purpose

Set the default interpolation type and order **(Macro only)**

### Description

"Basic Options" allows you to change the default type of
interpolation used to adapt two signals to a common sampling
frequency. Interpolation is used implicitly every time two signals
of unequal sampling period (scale) and/or x-axis-offset are
combined, so these changes have global effects on most of the
functions operating on more than one signal. **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.*
Parameters for "Basic 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.

### 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;

Note: The `order` parameter must be set for *every*
interpolation type (even if not used).

### Modules

Basic

### Related Functions

Spectral Options, Resample.

### References

Press et al. [16], Crochiere [17]