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84 lines
2.5 KiB
C
84 lines
2.5 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_std_f32.c
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* Description: Standard deviation of the elements of a floating-point vector
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*
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* $Date: 23 April 2021
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* $Revision: V1.9.0
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*
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* Target Processor: Cortex-M and Cortex-A cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "dsp/statistics_functions.h"
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/**
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@ingroup groupStats
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*/
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/**
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@defgroup STD Standard deviation
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Calculates the standard deviation of the elements in the input vector.
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The float implementation is relying on arm_var_f32 which is using a two-pass algorithm
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to avoid problem of numerical instabilities and cancellation errors.
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Fixed point versions are using the standard textbook algorithm since the fixed point
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numerical behavior is different from the float one.
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Algorithm for fixed point versions is summarized below:
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<pre>
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Result = sqrt((sumOfSquares - sum<sup>2</sup> / blockSize) / (blockSize - 1))
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sumOfSquares = pSrc[0] * pSrc[0] + pSrc[1] * pSrc[1] + ... + pSrc[blockSize-1] * pSrc[blockSize-1]
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sum = pSrc[0] + pSrc[1] + pSrc[2] + ... + pSrc[blockSize-1]
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</pre>
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There are separate functions for floating point, Q31, and Q15 data types.
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*/
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/**
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@addtogroup STD
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@{
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*/
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/**
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@brief Standard deviation of the elements of a floating-point vector.
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@param[in] pSrc points to the input vector
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@param[in] blockSize number of samples in input vector
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@param[out] pResult standard deviation value returned here
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@return none
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*/
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void arm_std_f32(
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const float32_t * pSrc,
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uint32_t blockSize,
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float32_t * pResult)
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{
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float32_t var;
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arm_var_f32(pSrc,blockSize,&var);
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arm_sqrt_f32(var, pResult);
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}
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/**
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@} end of STD group
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*/
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