CMSIS DSP Library from CMSIS 2.0. See http://www.onarm.com/cmsis/ for full details
Dependents: K22F_DSP_Matrix_least_square BNO055-ELEC3810 1BNO055 ECE4180Project--Slave2 ... more
Variance
[Statistics Functions]
Calculates the variance of the elements in the input vector. More...
Functions | |
void | arm_var_f32 (float32_t *pSrc, uint32_t blockSize, float32_t *pResult) |
Variance of the elements of a floating-point vector. | |
void | arm_var_q15 (q15_t *pSrc, uint32_t blockSize, q31_t *pResult) |
Variance of the elements of a Q15 vector. | |
void | arm_var_q31 (q31_t *pSrc, uint32_t blockSize, q63_t *pResult) |
Variance of the elements of a Q31 vector. |
Detailed Description
Calculates the variance of the elements in the input vector.
The underlying algorithm is used:
Result = (sumOfSquares - sum2 / blockSize) / (blockSize - 1)
where, sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1]
sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1]
There are separate functions for floating point, Q31, and Q15 data types.
Function Documentation
void arm_var_f32 | ( | float32_t * | pSrc, |
uint32_t | blockSize, | ||
float32_t * | pResult | ||
) |
Variance of the elements of a floating-point vector.
- Parameters:
-
[in] *pSrc points to the input vector [in] blockSize length of the input vector [out] *pResult variance value returned here
- Returns:
- none.
Definition at line 66 of file arm_var_f32.c.
void arm_var_q15 | ( | q15_t * | pSrc, |
uint32_t | blockSize, | ||
q31_t * | pResult | ||
) |
Variance of the elements of a Q15 vector.
- Parameters:
-
[in] *pSrc points to the input vector [in] blockSize length of the input vector [out] *pResult variance value returned here
- Returns:
- none.
Scaling and Overflow Behavior:
- The function is implemented using a 64-bit internal accumulator. The input is represented in 1.15 format. Intermediate multiplication yields a 2.30 format, and this result is added without saturation to a 64-bit accumulator in 34.30 format. With 33 guard bits in the accumulator, there is no risk of overflow, and the full precision of the intermediate multiplication is preserved. Finally, the 34.30 result is truncated to 34.15 format by discarding the lower 15 bits, and then saturated to yield a result in 1.15 format.
Definition at line 61 of file arm_var_q15.c.
void arm_var_q31 | ( | q31_t * | pSrc, |
uint32_t | blockSize, | ||
q63_t * | pResult | ||
) |
Variance of the elements of a Q31 vector.
- Parameters:
-
[in] *pSrc points to the input vector [in] blockSize length of the input vector [out] *pResult variance value returned here
- Returns:
- none.
Scaling and Overflow Behavior:
- The function is implemented using an internal 64-bit accumulator. The input is represented in 1.31 format, and intermediate multiplication yields a 2.62 format. The accumulator maintains full precision of the intermediate multiplication results, but provides only a single guard bit. There is no saturation on intermediate additions. If the accumulator overflows it wraps around and distorts the result. In order to avoid overflows completely the input signal must be scaled down by log2(blockSize) bits, as a total of blockSize additions are performed internally. Finally, the 2.62 accumulator is right shifted by 31 bits to yield a 1.31 format value.
Definition at line 63 of file arm_var_q31.c.
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