From cbc91bf6233a3a688a45426889ed650f13520467 Mon Sep 17 00:00:00 2001
From: "George L. F. Harris" <glfharris@gmail.com>
Date: Sun, 25 Feb 2024 22:36:58 +0000
Subject: [PATCH] Account for different volumes

Changed function one_second to account for the different volumes between
each compartment. Now calculates mass of drug moving via pathway:

(conc. * vol * rate constant - e.g. self.x2 * self.v2 * self.k21)

Then divides by the volume of the target compartment to calculate the
influence on concentration.
---
 PyTCI/models/base.py | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/PyTCI/models/base.py b/PyTCI/models/base.py
index 51139fb..26934c2 100644
--- a/PyTCI/models/base.py
+++ b/PyTCI/models/base.py
@@ -54,18 +54,18 @@ def wait_time(self, time_seconds):
         def one_second(self):
             """ time steps must be one second for accurate modelling """
 
-            x1k10 = self.x1 * self.k10
-            x1k12 = self.x1 * self.k12
-            x1k13 = self.x1 * self.k13
-            x2k21 = self.x2 * self.k21
-            x3k31 = self.x3 * self.k31
+            dx1dt = ((self.k21*self.x2*self.v2 + self.k31*self.x3*self.v3) \
+                    - (self.k10*self.x1*self.v1 + self.k12*self.x1*self.v1 + self.k13*self.x1*self.v1)) \
+                    / self.v1
+            dx2dt = (self.k12*self.x1*self.v1 - self.k21*self.x2*self.v2) / self.v2
+            dx3dt = (self.k13*self.x1*self.v1 - self.k31*self.x3*self.v3) / self.v3
 
             xk1e = self.x1 * self.keo
             xke1 = self.xeo * self.keo
 
-            self.x1 = self.x1 + (x2k21 - x1k12 + x3k31 - x1k13 - x1k10)
-            self.x2 = self.x2 + (x1k12 - x2k21)
-            self.x3 = self.x3 + (x1k13 - x3k31)
+            self.x1 += dx1dt
+            self.x2 += dx2dt
+            self.x3 += dx3dt
 
             self.xeo = self.xeo + (xk1e - xke1)