From b21b4c8dedc90d95aee684c1266f451ee071e2f8 Mon Sep 17 00:00:00 2001
From: Luc Maisonobe <luc@apache.org>
Date: Wed, 6 Jan 2016 12:24:24 +0100
Subject: [PATCH] The full set of derivatives are needed in Runge-Kutta.

---
 .../commons/math4/ode/nonstiff/RungeKuttaFieldIntegrator.java   | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/main/java/org/apache/commons/math4/ode/nonstiff/RungeKuttaFieldIntegrator.java b/src/main/java/org/apache/commons/math4/ode/nonstiff/RungeKuttaFieldIntegrator.java
index 598af3b41..eb0c08643 100644
--- a/src/main/java/org/apache/commons/math4/ode/nonstiff/RungeKuttaFieldIntegrator.java
+++ b/src/main/java/org/apache/commons/math4/ode/nonstiff/RungeKuttaFieldIntegrator.java
@@ -143,7 +143,7 @@ public abstract class RungeKuttaFieldIntegrator<T extends RealFieldElement<T>>
             interpolator.shift();
 
             // first stage
-            yDotK[0] = stepStart.getDerivative();
+            yDotK[0] = equations.getMapper().mapDerivative(stepStart);
 
             // next stages
             for (int k = 1; k < stages; ++k) {