text: /**
  * @license Apache-2.0
  *
  * Copyright (c) 2020 The Stdlib Authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *    http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
  
  #include "stdlib/stats/base/svariancetk.h"
  #include <stdint.h>
  
  /**
  * Computes the variance of a single-precision floating-point strided array using a one-pass textbook algorithm.
  *
  * @param N           number of indexed elements
  * @param correction  degrees of freedom adjustment
  * @param X           input array
  * @param stride      stride length
  * @return            output value
  */
  float stdlib_strided_svariancetk( const int64_t N, const float correction, const float *X, const int64_t stride ) {
  	int64_t ix;
  	int64_t i;
  	float S2;
  	float S;
  	float n;
  	float v;
  
  	n = (float)((double)N - (double)correction);
  	if ( N <= 0 || n <= 0 ) {
  		return 0.0f / 0.0f; // NaN
  	}
  	if ( N == 1 || stride == 0 ) {
  		return 0.0f;
  	}
  	if ( stride < 0 ) {
  		ix = (1-N) * stride;
  	} else {
  		ix = 0;
  	}
  	S2 = 0.0f;
  	S = 0.0f;
  	for ( i = 0; i < N; i++ ) {
  		v = X[ ix ];
  		S2 += v * v;
  		S += v;
  		ix += stride;
  	}
  	return (S2 - ((S/N)*S)) / n;
  }
  