fix：标准差计算优化

go.mod

@@ -48,6 +48,12 @@ require (
 	github.com/go-playground/validator/v10 v10.10.0 // indirect
 	github.com/go-sql-driver/mysql v1.7.0 // indirect
 	github.com/goccy/go-json v0.9.7 // indirect
+	github.com/gonum/blas v0.0.0-20181208220705-f22b278b28ac // indirect
+	github.com/gonum/floats v0.0.0-20181209220543-c233463c7e82 // indirect
+	github.com/gonum/internal v0.0.0-20181124074243-f884aa714029 // indirect
+	github.com/gonum/lapack v0.0.0-20181123203213-e4cdc5a0bff9 // indirect
+	github.com/gonum/matrix v0.0.0-20181209220409-c518dec07be9 // indirect
+	github.com/gonum/stat v0.0.0-20181125101827-41a0da705a5b // indirect
 	github.com/hashicorp/hcl v1.0.0 // indirect
 	github.com/jinzhu/inflection v1.0.0 // indirect
 	github.com/jinzhu/now v1.1.5 // indirect

go.sum

@@ -187,6 +187,18 @@ github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiu
 github.com/golang/snappy v0.0.0-20170215233205-553a64147049/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/golang/snappy v0.0.0-20180518054509-2e65f85255db/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/gomodule/redigo v2.0.0+incompatible/go.mod h1:B4C85qUVwatsJoIUNIfCRsp7qO0iAmpGFZ4EELWSbC4=
+github.com/gonum/blas v0.0.0-20181208220705-f22b278b28ac h1:Q0Jsdxl5jbxouNs1TQYt0gxesYMU4VXRbsTlgDloZ50=
+github.com/gonum/blas v0.0.0-20181208220705-f22b278b28ac/go.mod h1:P32wAyui1PQ58Oce/KYkOqQv8cVw1zAapXOl+dRFGbc=
+github.com/gonum/floats v0.0.0-20181209220543-c233463c7e82 h1:EvokxLQsaaQjcWVWSV38221VAK7qc2zhaO17bKys/18=
+github.com/gonum/floats v0.0.0-20181209220543-c233463c7e82/go.mod h1:PxC8OnwL11+aosOB5+iEPoV3picfs8tUpkVd0pDo+Kg=
+github.com/gonum/internal v0.0.0-20181124074243-f884aa714029 h1:8jtTdc+Nfj9AR+0soOeia9UZSvYBvETVHZrugUowJ7M=
+github.com/gonum/internal v0.0.0-20181124074243-f884aa714029/go.mod h1:Pu4dmpkhSyOzRwuXkOgAvijx4o+4YMUJJo9OvPYMkks=
+github.com/gonum/lapack v0.0.0-20181123203213-e4cdc5a0bff9 h1:7qnwS9+oeSiOIsiUMajT+0R7HR6hw5NegnKPmn/94oI=
+github.com/gonum/lapack v0.0.0-20181123203213-e4cdc5a0bff9/go.mod h1:XA3DeT6rxh2EAE789SSiSJNqxPaC0aE9J8NTOI0Jo/A=
+github.com/gonum/matrix v0.0.0-20181209220409-c518dec07be9 h1:V2IgdyerlBa/MxaEFRbV5juy/C3MGdj4ePi+g6ePIp4=
+github.com/gonum/matrix v0.0.0-20181209220409-c518dec07be9/go.mod h1:0EXg4mc1CNP0HCqCz+K4ts155PXIlUywf0wqN+GfPZw=
+github.com/gonum/stat v0.0.0-20181125101827-41a0da705a5b h1:fbskpz/cPqWH8VqkQ7LJghFkl2KPAiIFUHrTJ2O3RGk=
+github.com/gonum/stat v0.0.0-20181125101827-41a0da705a5b/go.mod h1:Z4GIJBJO3Wa4gD4vbwQxXXZ+WHmW6E9ixmNrwvs0iZs=
 github.com/google/btree v0.0.0-20180813153112-4030bb1f1f0c/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
 github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=

utils/calculate.go

@@ -164,28 +164,5 @@ func CalculationDecisive(sList []Coordinate) (r2 float64) {
 
 // CalculateStandardDeviation 计算标准差
 func CalculateStandardDeviation(data []float64) float64 {
-	// 计算平均值
-	mean := calculateMean(data)
-	// 计算方差
-	variance := calculateVariance(data, mean)
-	return math.Sqrt(variance)
-}
-
-// 计算平均值
-func calculateMean(data []float64) float64 {
-	sum := 0.0
-	for _, value := range data {
-		sum += value
-	}
-	return sum / float64(len(data))
-}
-
-// 计算方差
-func calculateVariance(data []float64, mean float64) float64 {
-	sumSquaredDiff := 0.0
-	for _, value := range data {
-		diff := value - mean
-		sumSquaredDiff += diff * diff
-	}
-	return sumSquaredDiff / float64(len(data))
+	return stat.StdDev(data, nil)
 }