Ejemplo n.º 1
0
//GridToGeodetic converts RT90 coordinates to WGS84
func GridToGeodetic(x, y float64) (float64, float64) {

	if CentralMeridian == 31337.0 {
		return 0.0, 0.0
	}

	e2 := Flattening * (2.0 - Flattening)
	n := Flattening / (2.0 - Flattening)
	a_roof := Axis / (1.0 + n) * (1.0 + n*n/4.0 + n*n*n*n/64.0)
	delta1 := n/2.0 - 2.0*n*n/3.0 + 37.0*n*n*n/96.0 - n*n*n*n/360.0
	delta2 := n*n/48.0 + n*n*n/15.0 - 437.0*n*n*n*n/1440.0
	delta3 := 17.0*n*n*n/480.0 - 37*n*n*n*n/840.0
	delta4 := 4397.0 * n * n * n * n / 161280.0

	Astar := e2 + e2*e2 + e2*e2*e2 + e2*e2*e2*e2
	Bstar := -(7.0*e2*e2 + 17.0*e2*e2*e2 + 30.0*e2*e2*e2*e2) / 6.0
	Cstar := (224.0*e2*e2*e2 + 889.0*e2*e2*e2*e2) / 120.0
	Dstar := -(4279.0 * e2 * e2 * e2 * e2) / 1260.0

	DegToRad := math.Pi / 180
	LambdaZero := CentralMeridian * DegToRad
	xi := (x - FalseNorthing) / (Scale * a_roof)
	eta := (y - FalseEasting) / (Scale * a_roof)
	xi_prim := xi - delta1*math.Sin(2.0*xi)*math.Cosh(2.0*eta) - delta2*math.Sin(4.0*xi)*math.Cosh(4.0*eta) - delta3*math.Sin(6.0*xi)*math.Cosh(6.0*eta) - delta4*math.Sin(8.0*xi)*math.Cosh(8.0*eta)
	eta_prim := eta - delta1*math.Cos(2.0*xi)*math.Sinh(2.0*eta) - delta2*math.Cos(4.0*xi)*math.Sinh(4.0*eta) - delta3*math.Cos(6.0*xi)*math.Sinh(6.0*eta) - delta4*math.Cos(8.0*xi)*math.Sinh(8.0*eta)
	phi_star := math.Asin(math.Sin(xi_prim) / math.Cosh(eta_prim))
	delta_lambda := math.Atan(math.Sinh(eta_prim) / math.Cos(xi_prim))
	lon_radian := LambdaZero + delta_lambda
	lat_radian := phi_star + math.Sin(phi_star)*math.Cos(phi_star)*(Astar+Bstar*math.Pow(math.Sin(phi_star), 2)+Cstar*math.Pow(math.Sin(phi_star), 4)+Dstar*math.Pow(math.Sin(phi_star), 6))

	return lat_radian * 180.0 / math.Pi, lon_radian * 180.0 / math.Pi
}
Ejemplo n.º 2
0
Archivo: tan.go Proyecto: gmwu/go
// Tanh 返回 x 的双曲正切。
func Tanh(x complex128) complex128 {
	d := math.Cosh(2*real(x)) + math.Cos(2*imag(x))
	if d == 0 {
		return Inf()
	}
	return complex(math.Sinh(2*real(x))/d, math.Sin(2*imag(x))/d)
}
Ejemplo n.º 3
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// https://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Tile_numbers_to_lon..2Flat.
func getLonLatFromTileName(x, y, zoom int64) Point {
	n := math.Pow(2, float64(zoom))
	lon := (float64(x) / n * 360) - 180
	latRad := math.Atan(math.Sinh(math.Pi * (1 - (2 * float64(y) / n))))
	lat := latRad * 180 / math.Pi

	return Point{lon, lat}
}
Ejemplo n.º 4
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func xyz_lonlat(x, y, z int) (lon, lat float64) {
	n := 1 << uint(z)
	fact := tilesize * float64(n)
	lon = float64(x)*360/fact - 180
	prj := (1 - float64(y)*2/fact)*math.Pi
	lat = rad_deg(math.Atan(math.Sinh(prj)))
	return
}
Ejemplo n.º 5
0
Archivo: sin.go Proyecto: gmwu/go
// 计算 sinh 和 cosh
func sinhcosh(x float64) (sh, ch float64) {
	if math.Abs(x) <= 0.5 {
		return math.Sinh(x), math.Cosh(x)
	}
	e := math.Exp(x)
	ei := 0.5 / e
	e *= 0.5
	return e - ei, e + ei
}
// SinH returns the Cosine of a given angle
func SinH(number float64) (float64, error) {

	if math.IsNaN(number) {
		return 0.0, errors.New("#VALUE!	-	Occurred because the supplied number argument is non-numeric")
	}

	// Sinh returns the hyperbolic sine of x.
	return math.Sinh(number), nil
}
Ejemplo n.º 7
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// Cot returns the cotangent of x.
func Cot(x complex128) complex128 {
	d := math.Cosh(2*imag(x)) - math.Cos(2*real(x))
	if math.Fabs(d) < 0.25 {
		d = tanSeries(x)
	}
	if d == 0 {
		return Inf()
	}
	return cmplx(math.Sin(2*real(x))/d, -math.Sinh(2*imag(x))/d)
}
Ejemplo n.º 8
0
Archivo: tan.go Proyecto: gmwu/go
// Tan 返回 x 的正切值。
func Tan(x complex128) complex128 {
	d := math.Cos(2*real(x)) + math.Cosh(2*imag(x))
	if math.Abs(d) < 0.25 {
		d = tanSeries(x)
	}
	if d == 0 {
		return Inf()
	}
	return complex(math.Sin(2*real(x))/d, math.Sinh(2*imag(x))/d)
}
Ejemplo n.º 9
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//GeodeticToGrid converts WGS84 coordinates to RT90
func GeodeticToGrid(lat, lon float64) (x, y float64) {

	// Prepare ellipsoid-based stuff.
	e2 := Flattening * (2.0 - Flattening)
	n := Flattening / (2.0 - Flattening)
	a_roof := Axis / (1.0 + n) * (1.0 + n*n/4.0 + n*n*n*n/64.0)
	A := e2
	B := (5.0*e2*e2 - e2*e2*e2) / 6.0
	C := (104.0*e2*e2*e2 - 45.0*e2*e2*e2*e2) / 120.0
	D := (1237.0 * e2 * e2 * e2 * e2) / 1260.0
	beta1 := n/2.0 - 2.0*n*n/3.0 + 5.0*n*n*n/16.0 + 41.0*n*n*n*n/180.0
	beta2 := 13.0*n*n/48.0 - 3.0*n*n*n/5.0 + 557.0*n*n*n*n/1440.0
	beta3 := 61.0*n*n*n/240.0 - 103.0*n*n*n*n/140.0
	beta4 := 49561.0 * n * n * n * n / 161280.0

	// Convert.
	DegToRad := math.Pi / 180.0
	phi := lat * DegToRad
	lambd := lon * DegToRad
	lambda_zero := CentralMeridian * DegToRad

	phi_star := phi - math.Sin(phi)*math.Cos(phi)*(A+
		B*math.Pow(math.Sin(phi), 2)+
		C*math.Pow(math.Sin(phi), 4)+
		D*math.Pow(math.Sin(phi), 6))
	delta_lambda := lambd - lambda_zero
	xi_prim := math.Atan(math.Tan(phi_star) / math.Cos(delta_lambda))
	eta_prim := math.Atanh(math.Cos(phi_star) * math.Sin(delta_lambda))
	x = Scale*a_roof*(xi_prim+
		beta1*math.Sin(2.0*xi_prim)*math.Cosh(2.0*eta_prim)+
		beta2*math.Sin(4.0*xi_prim)*math.Cosh(4.0*eta_prim)+
		beta3*math.Sin(6.0*xi_prim)*math.Cosh(6.0*eta_prim)+
		beta4*math.Sin(8.0*xi_prim)*math.Cosh(8.0*eta_prim)) +
		FalseNorthing
	y = Scale*a_roof*(eta_prim+
		beta1*math.Cos(2.0*xi_prim)*math.Sinh(2.0*eta_prim)+
		beta2*math.Cos(4.0*xi_prim)*math.Sinh(4.0*eta_prim)+
		beta3*math.Cos(6.0*xi_prim)*math.Sinh(6.0*eta_prim)+
		beta4*math.Cos(8.0*xi_prim)*math.Sinh(8.0*eta_prim)) +
		FalseEasting
	return x, y
}
Ejemplo n.º 10
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func XYToLonLat(xtile, ytile int, zoom uint) Point {
	var lon_deg, lat_deg float64
	var rt Point
	b := (1 << zoom)
	n := float64(b)
	lon_deg = (float64)(xtile*360)/n - 180
	lat_deg = math.Atan(math.Sinh(math.Pi*(1-2*(float64)(ytile)/n))) * 180 / math.Pi
	rt.lon = lon_deg
	rt.lat = lat_deg
	return rt
}
Ejemplo n.º 11
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// returns coordinates of central point of tile by tile-hash
func CentralPoint(hash int64) [2]float32 {
	z, x, y := HashtoZXY(hash)

	n := math.Pow(2, float64(z))

	lon_deg := ((float64(x)+0.5)/n)*360.0 - 180.0
	lat_rad := math.Atan(math.Sinh(math.Pi * (1 - (2*(float64(y)+0.5))/n)))
	lat_deg := lat_rad * (180.0 / math.Pi)

	return [2]float32{float32(lat_deg), float32(lon_deg)}
}
Ejemplo n.º 12
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func TestMathSinh(t *testing.T) {
	// This is just an interface to Go's function, so just a quick simple test
	ctx := runtime.NewCtx(nil, nil)
	mm := new(MathMod)
	mm.SetCtx(ctx)
	val := 1.12
	ret := mm.math_Sinh(runtime.Number(val))
	exp := math.Sinh(val)
	if ret.Float() != exp {
		t.Errorf("expected %f, got %f", exp, ret.Float())
	}
}
//CscH Returns the hyperbolic cosecant of an angle
func CscH(number float64) (float64, error) {

	if number == 0 {
		return 0.0, errors.New("#DIV/0!	-	Occurred because the supplied number argument is equal to zero")
	}

	if number < -134217728 || number > 134217728 {
		return 0.0, errors.New("#NUM! -  Occurred because the supplied number argument is less than -2^27 or is greater than 2^27")
	}

	if math.IsNaN(number) {
		return 0.0, errors.New("#VALUE!	-	Occurred because the supplied number argument is non-numeric")
	}

	return 1 / math.Sinh(number), nil
}
Ejemplo n.º 14
0
// Func SinK computes the curvature dependent distance
func SinK(omkh2, d float64) float64 {
	k := math.Sqrt(math.Abs(omkh2))
	kd := k * d
	var ret float64
	switch {
	case (omkh2 > 0) && (kd > 1.e-2):
		ret = math.Sinh(kd) / k
	case (omkh2 < 0) && (kd > 1.e-2):
		ret = math.Sin(kd) / k
	case (omkh2 >= 0) && (kd < 1.e-2):
		ret = d + kd*kd*d/6
	case (omkh2 < 0) && (kd < 1.e-2):
		ret = d - kd*kd*d/6
	}
	return ret
}
Ejemplo n.º 15
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// that will only work well +-10 degrees around longitude 0.
var TransverseMercator = Projection{
	Project: func(p *Point) {
		radLat := deg2rad(p.Lat())
		radLng := deg2rad(p.Lng())

		sincos := math.Sin(radLng) * math.Cos(radLat)
		p.SetX(0.5 * math.Log((1+sincos)/(1-sincos)) * EarthRadius)

		p.SetY(math.Atan(math.Tan(radLat)/math.Cos(radLng)) * EarthRadius)
	},
	Inverse: func(p *Point) {
		x := p.X() / EarthRadius
		y := p.Y() / EarthRadius

		lng := math.Atan(math.Sinh(x) / math.Cos(y))
		lat := math.Asin(math.Sin(y) / math.Cosh(x))

		p.SetLng(rad2deg(lng))
		p.SetLat(rad2deg(lat))
	},
}

// ScalarMercator converts from lng/lat float64 to x,y uint64.
// This is the same as Google's world coordinates.
var ScalarMercator struct {
	Level   uint64
	Project func(lng, lat float64, level ...uint64) (x, y uint64)
	Inverse func(x, y uint64, level ...uint64) (lng, lat float64)
}
Ejemplo n.º 16
0
// Inverse transverse mercator projection: Projection of an cylinder onto the surface of
// of an ellipsoid. Also known as reverse Gauss-Krüger projection. Input parameters:
//
//	pt *GeoPoint: Easting(Y) and Northing(X) of map point to be projected; in meters
//	latO, longO: Shifted origin of latitude and longitude in decimal degrees
//	fe, fn: False easting and northing respectively in meters
//	scale: Projection scaling; Dimensionless, typically 1 or little bellow
//
// This algorithm uses the algorithm described by Redfearn
// http://en.wikipedia.org/wiki/Transverse_Mercator:_Redfearn_series
//
// Taken from "OGP Publication 373-7-2 – Surveying and Positioning Guidance Note number 7, part 2 – November 2010",
// pp. 48 - 51
//
// More accurate, iterative but slower algorithmic implementation
func InverseTransverseMercator(pt *GeoPoint, latO, longO, scale, fe, fn float64) *PolarCoord {

	var gc PolarCoord

	el := pt.El

	latOrad := degtorad(latO)
	longOrad := degtorad(longO)

	f := 1 - el.b/el.a
	esq := math.Sqrt(2.0*f - f*f)

	n := f / (2.0 - f)
	B := (el.a / (1 + n)) * (1 + n*n/4.0 + n*n*n*n/64.0)

	var SO float64

	if latOrad != 0.0 {

		h1 := n/2.0 - (2.0/3.0)*n*n + (5.0/16.0)*n*n*n + (41.0/180.0)*n*n*n*n
		h2 := (13.0/48.0)*n*n - (3.0/5.0)*n*n*n + (557.0/1440.0)*n*n*n*n
		h3 := (61.0/240.0)*n*n*n - (103.0/140.0)*n*n*n*n
		h4 := (49561.0 / 161280.0) * n * n * n * n

		QO := math.Asinh(math.Tan(latOrad)) - (esq * math.Atanh(esq*math.Sin(latOrad)))
		bO := math.Atan(math.Sinh(QO))
		xiO0 := bO // math.Asin(math.Sin(bO))

		xiO1 := h1 * math.Sin(2.0*xiO0)
		xiO2 := h2 * math.Sin(4.0*xiO0)
		xiO3 := h3 * math.Sin(6.0*xiO0)
		xiO4 := h4 * math.Sin(8.0*xiO0)

		xiO := xiO0 + xiO1 + xiO2 + xiO3 + xiO4

		SO = B * xiO
	}

	h1i := n/2.0 - (2.0/3.0)*n*n + (37.0/96.0)*n*n*n - (1.0/360.0)*n*n*n*n
	h2i := (1.0/48.0)*n*n + (1.0/15.0)*n*n*n - (437.0/1440.0)*n*n*n*n
	h3i := (17.0/480.0)*n*n*n - (37.0/840.0)*n*n*n*n
	h4i := (4397.0 / 161280.0) * n * n * n * n

	etai := (pt.X - fe) / (B * scale)
	xii := ((pt.Y - fn) + scale*SO) / (B * scale)

	xi1i := h1i * math.Sin(2*xii) * math.Cosh(2*etai)
	xi2i := h2i * math.Sin(4*xii) * math.Cosh(4*etai)
	xi3i := h3i * math.Sin(6*xii) * math.Cosh(6*etai)
	xi4i := h4i * math.Sin(8*xii) * math.Cosh(8*etai)

	eta1i := h1i * math.Cos(2*xii) * math.Sinh(2*etai)
	eta2i := h2i * math.Cos(4*xii) * math.Sinh(4*etai)
	eta3i := h3i * math.Cos(6*xii) * math.Sinh(6*etai)
	eta4i := h4i * math.Cos(8*xii) * math.Sinh(8*etai)

	xi0i := xii - (xi1i + xi2i + xi3i + xi4i)
	eta0i := etai - (eta1i + eta2i + eta3i + eta4i)

	bi := math.Asin(math.Sin(xi0i) / math.Cosh(eta0i))

	Qi := math.Asinh(math.Tan(bi))
	Qiiold := Qi + (esq * math.Atanh(esq*math.Tanh(Qi)))
	Qii := Qi + (esq * math.Atanh(esq*math.Tanh(Qiiold)))

	for math.Abs(Qiiold-Qii) > 1e-12 {
		Qiiold = Qii
		Qii = Qi + (esq * math.Atanh(esq*math.Tanh(Qiiold)))
	}

	gc.Latitude = radtodeg(math.Atan(math.Sinh(Qii)))
	gc.Longitude = radtodeg(longOrad + math.Asin(math.Tanh(eta0i)/math.Cos(bi)))

	gc.El = el

	return &gc
}
Ejemplo n.º 17
0
// Direct transverse mercator projection: Projection of an ellipsoid onto the surface of
// of a cylinder. Also known as Gauss-Krüger projection. Input parameters:
//
//	gc *PolarCoord: Latitude and Longitude or point to be projected; in decimal degrees
//	latO, longO: Shifted origin of latitude and longitude in decimal degrees
//	fe, fn: False easting and northing respectively in meters
//	scale: Projection scaling; Dimensionless, typically 1 or little bellow
//
// This algorithm uses the algorithm described by Redfearn
// http://en.wikipedia.org/wiki/Transverse_Mercator:_Redfearn_series
//
// Taken from "OGP Publication 373-7-2 – Surveying and Positioning Guidance Note number 7, part 2 – November 2010",
// pp. 48 - 51
func DirectTransverseMercator(gc *PolarCoord, latO, longO, scale, fe, fn float64) *GeoPoint {

	var pt GeoPoint

	el := gc.El

	latOrad := degtorad(latO)
	longOrad := degtorad(longO)

	latrad := degtorad(gc.Latitude)
	longrad := degtorad(gc.Longitude)

	f := 1 - el.b/el.a
	esq := math.Sqrt(2.0*f - f*f)

	n := f / (2.0 - f)
	B := (el.a / (1 + n)) * (1 + n*n/4.0 + n*n*n*n/64.0)

	h1 := n/2.0 - (2.0/3.0)*(n*n) + (5.0/16.0)*(n*n*n) + (41.0/180.0)*(n*n*n*n)
	h2 := (13.0/48.0)*(n*n) - (3.0/5.0)*(n*n*n) + (557.0/1440.0)*(n*n*n*n)
	h3 := (61.0/240.0)*(n*n*n) - (103.0/140.0)*(n*n*n*n)
	h4 := (49561.0 / 161280.0) * (n * n * n * n)

	var SO float64

	if latOrad != 0.0 {
		QO := math.Asinh(math.Tan(latOrad)) - (esq * math.Atanh(esq*math.Sin(latOrad)))
		bO := math.Atan(math.Sinh(QO))
		xiO0 := bO // math.Asin(math.Sin(bO))

		xiO1 := h1 * math.Sin(2.0*xiO0)
		xiO2 := h2 * math.Sin(4.0*xiO0)
		xiO3 := h3 * math.Sin(6.0*xiO0)
		xiO4 := h4 * math.Sin(8.0*xiO0)

		xiO := xiO0 + xiO1 + xiO2 + xiO3 + xiO4

		SO = B * xiO
	}

	Q := math.Asinh(math.Tan(latrad)) - (esq * math.Atanh(esq*math.Sin(latrad)))
	b := math.Atan(math.Sinh(Q))

	eta0 := math.Atanh(math.Cos(b) * math.Sin(longrad-longOrad))
	xi0 := math.Asin(math.Sin(b) * math.Cosh(eta0))

	xi1 := h1 * math.Sin(2*xi0) * math.Cosh(2*eta0)
	xi2 := h2 * math.Sin(4*xi0) * math.Cosh(4*eta0)
	xi3 := h3 * math.Sin(6*xi0) * math.Cosh(6*eta0)
	xi4 := h4 * math.Sin(8*xi0) * math.Cosh(8*eta0)
	xi := xi0 + xi1 + xi2 + xi3 + xi4

	eta1 := h1 * math.Cos(2*xi0) * math.Sinh(2*eta0)
	eta2 := h2 * math.Cos(4*xi0) * math.Sinh(4*eta0)
	eta3 := h3 * math.Cos(6*xi0) * math.Sinh(6*eta0)
	eta4 := h4 * math.Cos(8*xi0) * math.Sinh(8*eta0)
	eta := eta0 + eta1 + eta2 + eta3 + eta4

	pt.X = fe + scale*B*eta
	pt.Y = fn + scale*(B*xi-SO)

	pt.El = el

	return &pt
}
Ejemplo n.º 18
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func mathSinh(L *LState) int {
	L.Push(LNumber(math.Sinh(float64(L.CheckNumber(1)))))
	return 1
}
Ejemplo n.º 19
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//Y2Lat transforms y into a latitude in degree at a given level.
func Y2Lat(level int, y int) float64 {
	var yosm = y

	latitudeRad := math.Atan(math.Sinh(math.Pi * (1. - 2.*float64(yosm)/float64(n(level)))))
	return -(latitudeRad * 180.0 / math.Pi)
}
Ejemplo n.º 20
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func LongRunningFuncion() {
	for i := 0; i < LONG; i++ {
		math.Sinh(float64(i))
	}
}
Ejemplo n.º 21
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func TilePos2LL(x float64, y float64) (lat float64, lon float64) {
	var tilesOnOneEdge float64 = math.Pow(2.0, zoomLevel)
	lon = (x * (360 / (tilesOnOneEdge))) - 180
	lat = rad2deg * (math.Atan(math.Sinh((1 - y*(2/(tilesOnOneEdge))) * math.Pi)))
	return
}
Ejemplo n.º 22
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//define the integral of the kernel
func K(t float64) float64 {
	return math.Sinh(t)
}
Ejemplo n.º 23
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func FunctionVal(f Function, x float64) float64 {
	//
	switch f {
	case Floor:
		i, _ := math.Modf(x)
		return i
	case Fract:
		_, f := math.Modf(x)
		return f
	case Chs:
		return -x
	case Rec:
		if x == 0 { // TODO
			return math.NaN()
		}
		return 1 / x
	case Sqr:
		return x * x
	case Sqrt:
		return math.Sqrt(x)
	case Exp:
		return math.Exp(x)
	case Exp10:
		return math.Exp(x * math.Ln10)
	case Exp2:
		return math.Exp(x * math.Ln2)
	case Log:
		return math.Log(x)
	case Lg:
		return math.Log10(x)
	case Ld:
		return math.Log2(x)
	case Sin:
		return math.Sin(x)
	case Cos:
		return math.Cos(x)
	case Tan:
		return math.Tan(x)
	case Cot:
		return 1 / math.Tan(x)
	case Arcsin:
		return math.Asin(x)
	case Arccos:
		return math.Acos(x)
	case Arctan:
		return math.Atan(x)
	case Arccot:
		return math.Atan(x)
	case Sinh:
		return math.Sinh(x)
	case Cosh:
		return (math.Exp(x) + math.Exp(-x)) / 2
	case Tanh:
		return math.Tanh(x)
	case Coth:
		return (math.Exp(x) + math.Exp(-x)) / (math.Exp(x) - math.Exp(-x))
	case Arsinh:
		return math.Asinh(x)
	case Arcosh:
		return math.Log(x + math.Sqrt(x*x-1))
	case Artanh:
		return math.Atanh(x)
	case Arcoth:
		return math.Log((x+1)/(x-1)) / 2
	case Gamma:
		return math.Gamma(x)
	}
	return math.NaN()
}
Ejemplo n.º 24
0
// float32 version of math.Sinhf
func Sinh(x float32) float32 {
	return float32(math.Sinh(float64(x)))
}
Ejemplo n.º 25
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func (m *MathMod) math_Sinh(args ...runtime.Val) runtime.Val {
	runtime.ExpectAtLeastNArgs(1, args)
	return runtime.Number(math.Sinh(args[0].Float()))
}
Ejemplo n.º 26
0
Archivo: voice.go Proyecto: acshi/acshi
// Chebyshev biquad (2-poles) recursive coefficients
// Adapted from The Scientist and Engineer's Guide to Digital Signal Processing, Steven W. Smith
// poleIndex = [0, poleCount)
// percentRipple in the pass band can range from 0 for a butterworth to about 0.29. Something like 0.005 is a good trade-off.
func chebyshevBiquad(freq, percentRipple float64, poleIndex, poleCount int, highpass bool) (stageAs, stageBs []float64) {
	// We start off by designing a low-pass filter with unity cut-off frequency

	// Location of pole on unit circle, real and imaginary parts
	// The maximally flat butterworth filter positions the poles so that
	// they form a semi-circle on the left side of the s-plane (sigma < 0)
	// The half offset keeps the poles evenly spaced and off of the sigma=0 line
	// s-plane s = sigma + i * omega = poleR + i * poleI
	poleI, poleR := math.Sincos((float64(poleIndex) + 0.5) * math.Pi / float64(poleCount))
	poleR = -poleR

	// The chebyshev filter uses an ellipse to move all of the poles closer to the sigma=0 line
	// This causes pass-band ripple and sharpens the drop off
	// Warp coordinates from being on a circle to an ellipse
	if percentRipple != 0.0 {
		e := math.Sqrt(1/((1-percentRipple)*(1-percentRipple)) - 1)
		v := math.Asinh(1/e) / float64(poleCount)
		k := math.Acosh(1/e) / float64(poleCount)

		k = math.Cosh(k)

		poleR = poleR * math.Sinh(v) / k
		poleI = poleI * math.Cosh(v) / k
	}

	// bilinear s-domain to z-domain transformation
	t := 2 * math.Tan(0.5)
	w := 2 * math.Pi * freq
	m := poleR*poleR + poleI*poleI
	d := 4 - 4*poleR*t + m*t*t
	x0 := t * t / d
	x1 := 2 * t * t / d
	x2 := t * t / d
	y1 := (8 - 2*m*t*t) / d
	y2 := (-4 - 4*poleR*t - m*t*t) / d

	// We now have the coefficients of a low-pass filter with a cutoff frequency of 1 (2 times the nyquist)...
	// We must now apply our desired frequency and convert to a high-pass filter if necessary
	// as with the bilinear tranform, these are the results of a substitution in the transfer function...

	var k float64
	if highpass {
		k = -math.Cos(w/2+0.5) / math.Cos(w/2-0.5)
	} else {
		k = math.Sin(0.5-w/2) / math.Sin(0.5+w/2)
	}

	d = 1 + (y1*k - y2*k*k)
	a0 := (x0 - x1*k + x2*k*k) / d
	a1 := (-2*x0*k + x1 + (x1*k*k - 2*x2*k)) / d
	a2 := (x0*k*k - x1*k + x2) / d
	b1 := (2*k + y1 + y1*k*k - 2*y2*k) / d
	b2 := (-k*k - y1*k + y2) / d
	if highpass {
		a1, b1 = -a1, -b1
	}

	// we now have the desired coefficients of our low/high pass filter with the desired cutoff frequency
	// however, the gain has not been normalized, if that is desired...

	stageAs = []float64{a0, a1, a2}
	stageBs = []float64{0, b1, b2}
	return
}
Ejemplo n.º 27
0
//func (*Tile) Num2deg(t *Tile) (lat float64, lon float64) {
func Num2deg(t *Tile) (lat float64, lon float64) {
	n := math.Exp2(float64(t.Z))
	lat = 180.0 / math.Pi * math.Atan(math.Sinh(math.Pi*(1-2*float64(t.Y)/n)))
	lon = float64(t.X)/n*360.0 - 180.0
	return lat, lon
}