Computes the standard deviation value of a vector.
Syntax
IppStatus ippsStdDev_32f(const Ipp32f* pSrc, int len, Ipp32f* pStdDev, IppHintAlgorithm hint);
IppStatus ippsStdDev_64f(const Ipp64f* pSrc, int len, Ipp64f* pStdDev);
IppStatus ippsStdDev_16s32s_Sfs(const Ipp16s* pSrc, int len, Ipp32s* pStdDev, int scaleFactor);
IppStatus ippsStdDev_16s_Sfs(const Ipp16s* pSrc, int len, Ipp16s* pStdDev, int scaleFactor);
Parameters
pSrc |
Pointer to the source vector. |
pStdDev |
Pointer to the output result. |
len |
Number of elements in the vector. |
hint |
Suggests using specific code. The possible values for the hint argument are described in Hint Arguments. |
scaleFactor |
Scale factor, refer to Integer Scaling. |
Description
The function ippsStdDev is declared in the ipps.h file. This function computes the standard deviation of the input vector pSrc, and stores the result in pStdDev. The vector length can not be less than 2. The standard deviation of pSrc is defined by the unbiased estimate formula:
The hint argument suggests using specific code, either faster but less accurate calculation, or more accurate but slower calculation.
The example below shows how to use the function ippsStdDev_32f.
Return Values
ippStsNoErr |
Indicates no error. |
ippStsNullPtrErr |
Indicates an error when the pStdDev or pSrc pointer is NULL. |
ippStsSizeErr |
Indicates an error when len is less than or equal to 1. |
Using the ippsStdDev Function
void stdev(void) {
Ipp32f *x = ippsMalloc_32f(1000), stdev;
int i;
for (i = 0; i<1000; ++i) x[i] = (float)rand() / RAND_MAX;
ippsStdDev_32f(x, 1000, &stdev, ippAlgHintFast);
printf_32f(“stdev =”, &stdev, 1, ippStsNoErr);
ippsFree(x);
}
Output:
stdev = 0.286813
Matlab* Analog:
>> x = rand(1,1000); std(x)