From 0d4dcdc1c4717c88e79dfd0b7d4ebe34ff7cc548 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 6 Jun 2019 00:22:10 +0300
Subject: [PATCH] Add a simple linearly interpolated "spline"

---
 source/interpolate/linearspline.h | 42 +++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 source/interpolate/linearspline.h

diff --git a/source/interpolate/linearspline.h b/source/interpolate/linearspline.h
new file mode 100644
index 0000000..2c88ceb
--- /dev/null
+++ b/source/interpolate/linearspline.h
@@ -0,0 +1,42 @@
+#ifndef MSP_INTERPOLATE_LINEARSPLINE_H_
+#define MSP_INTERPOLATE_LINEARSPLINE_H_
+
+#include <vector>
+#include "spline.h"
+
+namespace Msp {
+namespace Interpolate {
+
+/**
+A very simple type of spline.  It interpolates the value linearly between
+knots.
+*/
+template<typename T, unsigned N = 1>
+class LinearSpline: public Spline<T, 1, N>
+{
+public:
+	using typename Spline<T, 1, N>::Value;
+	using typename Spline<T, 1, N>::Knot;
+
+	LinearSpline(const std::vector<Knot> &k):
+		Spline<T, 1, N>(k.front())
+	{
+		typedef SplineValue<T, N> SV;
+
+		this->reserve(k.size()-1);
+		for(unsigned i=1; i<k.size(); ++i)
+		{
+			T dx = k[i].x-k[i-1].x;
+			Value slope = (k[i].y-k[i-1].y)/dx;
+			Polynomial<T, 1> p[N];
+			for(unsigned j=0; j<N; ++j)
+				p[j] = Polynomial<T, 1>(LinAl::Vector<T, 2>(SV::get(slope, j), SV::get(k[i-1].y, j)-k[i-1].x*SV::get(slope, j)));
+			this->add_segment(p, k[i].x);
+		}
+	}
+};
+
+} // namespace Interpolate
+} // namespace Msp
+
+#endif
-- 
2.43.0