From d7246b05b1f4d9c0e9c42741febe69d3a022b4c9 Mon Sep 17 00:00:00 2001
From: Cory <cory@balaton.dev>
Date: Tue, 17 Oct 2023 17:31:56 +0200
Subject: [PATCH] Fix last update of RK4

---
 src/PenningTrap.cpp | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/PenningTrap.cpp b/src/PenningTrap.cpp
index ae8903b..ab99599 100644
--- a/src/PenningTrap.cpp
+++ b/src/PenningTrap.cpp
@@ -53,8 +53,8 @@ vec_3d PenningTrap::v_func(unsigned int i, unsigned int j, double dt)
     case 2:
         return dt * this->k_v[2][j];
     case 3:
-        return (dt / 6.) * (this->k_v[0][j] + this->k_v[1][j] +
-                            this->k_v[2][j] + this->k_v[3][j]);
+        return (dt / 6.) * (this->k_v[0][j] + 2.*this->k_v[1][j] +
+                            2.*this->k_v[2][j] + this->k_v[3][j]);
     default:
         std::cout << "Not valid!" << std::endl;
         abort();
@@ -71,8 +71,8 @@ vec_3d PenningTrap::r_func(unsigned int i, unsigned int j, double dt)
     case 2:
         return dt * this->k_r[2][j];
     case 3:
-        return (dt / 6.) * (this->k_r[0][j] + this->k_r[1][j] +
-                            this->k_r[2][j] + this->k_r[3][j]);
+        return (dt / 6.) * (this->k_r[0][j] + 2.*this->k_r[1][j] +
+                            2.*this->k_r[2][j] + this->k_r[3][j]);
     default:
         std::cout << "Not valid!" << std::endl;
         abort();