From 355181843fa7dd60333c81731695d593ce249623 Mon Sep 17 00:00:00 2001
From: Ron Evans <ron@hybridgroup.com>
Date: Wed, 15 Aug 2018 17:06:52 +0200
Subject: [PATCH] core: add Rescale utility function for straight linear
 rescaling

Signed-off-by: Ron Evans <ron@hybridgroup.com>
---
 utils.go      | 5 +++++
 utils_test.go | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/utils.go b/utils.go
index d5830a46..46d5909b 100644
--- a/utils.go
+++ b/utils.go
@@ -57,6 +57,11 @@ func ToScale(input, min, max float64) float64 {
 	}
 }
 
+// Rescale performs a direct linear rescaling of a number from one scale to another.
+func Rescale(input, fromMin, fromMax, toMin, toMax float64) float64 {
+	return (input-fromMin)*(toMax-toMin)/(fromMax-fromMin) + toMin
+}
+
 // DefaultName returns a sensible random default name
 // for a robot, adaptor or driver
 func DefaultName(name string) string {
diff --git a/utils_test.go b/utils_test.go
index 33e22b3d..6f58cb5b 100644
--- a/utils_test.go
+++ b/utils_test.go
@@ -73,6 +73,11 @@ func TestToScale(t *testing.T) {
 	gobottest.Assert(t, ToScale(0.5, 0, 10), 5.0)
 }
 
+func TestRescale(t *testing.T) {
+	gobottest.Assert(t, Rescale(500, 0, 1000, 0, 10), 5.0)
+	gobottest.Assert(t, Rescale(-1.0, -1, 0, 490, 350), 490.0)
+}
+
 func TestRand(t *testing.T) {
 	a := Rand(10000)
 	b := Rand(10000)