A first functional version of obiclean

pkg/obistats/utils.go

@@ -0,0 +1,49 @@
+package obistats
+
+import (
+	log "github.com/sirupsen/logrus"
+	"math"
+)
+
+// Lchoose returns logarithms of binomial coefficients
+func Lchoose(n,x int) float64 {
+	fn := float64(n)
+	fx := float64(x)
+
+	ln1, _ := math.Lgamma(fn + 1.0)
+	lx1, _ := math.Lgamma(fx + 1.0)
+	lnx1, _ := math.Lgamma(fn - fx + 1.0)
+
+	return ln1 - lx1 - lnx1
+}
+
+func Choose(n,x int) float64 {
+	return math.Exp(Lchoose(x,n))
+}
+
+
+func LogAddExp(x, y float64) float64 {
+
+	tmp := x - y
+  
+	if tmp > 0 {
+  
+	  return x + math.Log1p(math.Exp(-tmp))
+  
+	} else if tmp <= 0 {
+  
+	  return y + math.Log1p(math.Exp(tmp))
+  
+	} else {
+  
+	  // Nans, or infinities of the same sign involved
+  
+	  log.Errorf("logaddexp %f %f", x, y)
+  
+	  return x + y
+  
+	}
+  
+  }
+  
+