Linear Interpolation

Linear interpolation is a method of curve fitting using linear polynomials. More...

Collaboration diagram for Linear Interpolation:

Functions
__STATIC_INLINE float32_t	arm_linear_interp_f32 (arm_linear_interp_instance_f32 *S, float32_t x)
	Process function for the floating-point Linear Interpolation Function.
__STATIC_INLINE q15_t	arm_linear_interp_q15 (q15_t *pYData, q31_t x, uint32_t nValues)
	Process function for the Q15 Linear Interpolation Function.
__STATIC_INLINE q31_t	arm_linear_interp_q31 (q31_t *pYData, q31_t x, uint32_t nValues)
	Process function for the Q31 Linear Interpolation Function.
__STATIC_INLINE q7_t	arm_linear_interp_q7 (q7_t *pYData, q31_t x, uint32_t nValues)
	Process function for the Q7 Linear Interpolation Function.

Detailed Description

Linear interpolation is a method of curve fitting using linear polynomials.

Linear interpolation works by effectively drawing a straight line between two neighboring samples and returning the appropriate point along that line

Linear interpolation

A Linear Interpolate function calculates an output value(y), for the input(x) using linear interpolation of the input values x0, x1( nearest input values) and the output values y0 and y1(nearest output values)

Algorithm:

      y = y0 + (x - x0) * ((y1 - y0)/(x1-x0))
      where x0, x1 are nearest values of input x
            y0, y1 are nearest values to output y

This set of functions implements Linear interpolation process for Q7, Q15, Q31, and floating-point data types. The functions operate on a single sample of data and each call to the function returns a single processed value. S points to an instance of the Linear Interpolate function data structure. x is the input sample value. The functions returns the output value.

if x is outside of the table boundary, Linear interpolation returns first value of the table if x is below input range and returns last value of table if x is above range.

Function Documentation

__STATIC_INLINE float32_t arm_linear_interp_f32	(	arm_linear_interp_instance_f32 *	S,
		float32_t	x
	)

Process function for the floating-point Linear Interpolation Function.

Parameters

[in,out]	*S	is an instance of the floating-point Linear Interpolation structure
[in]	x	input sample to process

Returns

y processed output sample.

Definition at line 5869 of file arm_math.h.

References arm_linear_interp_instance_f32::nValues, arm_linear_interp_instance_f32::pYData, arm_linear_interp_instance_f32::x1, and arm_linear_interp_instance_f32::xSpacing.

__STATIC_INLINE q15_t arm_linear_interp_q15	(	q15_t *	pYData,
		q31_t	x,
		uint32_t	nValues
	)

Process function for the Q15 Linear Interpolation Function.

Parameters

[in]	*pYData	pointer to Q15 Linear Interpolation table
[in]	x	input sample to process
[in]	nValues	number of table values

Returns

y processed output sample.

Input sample x is in 12.20 format which contains 12 bits for table index and 20 bits for fractional part. This function can support maximum of table size 2^12.

Definition at line 5990 of file arm_math.h.

__STATIC_INLINE q31_t arm_linear_interp_q31	(	q31_t *	pYData,
		q31_t	x,
		uint32_t	nValues
	)

Process function for the Q31 Linear Interpolation Function.

Parameters

[in]	*pYData	pointer to Q31 Linear Interpolation table
[in]	x	input sample to process
[in]	nValues	number of table values

Returns

y processed output sample.

Input sample x is in 12.20 format which contains 12 bits for table index and 20 bits for fractional part. This function can support maximum of table size 2^12.

Definition at line 5928 of file arm_math.h.

__STATIC_INLINE q7_t arm_linear_interp_q7	(	q7_t *	pYData,
		q31_t	x,
		uint32_t	nValues
	)

Process function for the Q7 Linear Interpolation Function.

Parameters

[in]	*pYData	pointer to Q7 Linear Interpolation table
[in]	x	input sample to process
[in]	nValues	number of table values

Returns

y processed output sample.

Input sample x is in 12.20 format which contains 12 bits for table index and 20 bits for fractional part. This function can support maximum of table size 2^12.

Definition at line 6050 of file arm_math.h.