From 6353e6b32965abfa30da2d49ffde0b09a25d731c Mon Sep 17 00:00:00 2001
From: Mark Liversedge <liversedge@gmail.com>
Date: Tue, 5 Nov 2013 18:54:06 +0000
Subject: [PATCH] Add aPower

Introduce altitude adjusted power 'aPower'.

This is a new ride data series that takes into account
the effect of altitude on power output.

At present we are only adding this as a derived data series
with the intention of making it possible to plot it on
the ride chart.

We will also introduce alternate metrics for average power,
bikescore etc that are based upon the aPower value.
---
 src/RideFile.cpp | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/src/RideFile.cpp b/src/RideFile.cpp
index 1825e0204..cf34fe016 100644
--- a/src/RideFile.cpp
+++ b/src/RideFile.cpp
@@ -923,6 +923,11 @@ RideFile::recalculateDerivedSeries()
     double XPtotal = 0.0;
     int XPcount = 0;
 
+    //
+    // APower Initialisation -- working variables
+    double APtotal=0;
+    double APcount=0;
+
     foreach(RideFilePoint *p, dataPoints_) {
 
         //
@@ -988,7 +993,42 @@ RideFile::recalculateDerivedSeries()
         if (p->xp < minPoint->xp) minPoint->xp = p->xp;
 
         // aPower
-        // XXX coming soon.
+        if (dataPresent.watts == true && dataPresent.alt == true) {
+
+            dataPresent.apower = true;
+
+            static const double a0  = -174.1448622;
+            static const double a1  = 1.0899959;
+            static const double a2  = -0.0015119;
+            static const double a3  = 7.2674E-07;
+            static const double E = 2.71828183;
+
+            if (p->alt > 0) {
+                // pbar [mbar]= 0.76*EXP( -alt[m] / 7000 )*1000 
+                double pbar = 0.76 * pow(E, p->alt / 7000) * 1000;
+
+                // %Vo2max= a0 + a1 * pbar + a2 * pbar ^2 + a3 * pbar ^3 (with pbar in mbar)
+                double vo2maxPCT = a0 + (a1 * pbar) + (a2 * pow(pbar,2)) + (a3 * pow(pbar,3)); 
+
+                p->apower = p->watts / vo2maxPCT * 100.00f;
+
+            } else {
+
+                p->apower = p->watts;
+            }
+
+        } else {
+
+            dataPresent.apower = false;
+            p->apower = 0.00f;
+        }
+
+        // now the min and max values for NP
+        if (p->apower > maxPoint->apower) maxPoint->apower = p->apower;
+        if (p->apower < minPoint->apower) minPoint->apower = p->apower;
+
+        APtotal += p->apower;
+        APcount++;
     }
 
     // Averages and Totals
@@ -998,6 +1038,9 @@ RideFile::recalculateDerivedSeries()
     avgPoint->xp = XPcount ? (XPtotal / XPcount) : 0;
     totalPoint->xp = XPtotal;
 
+    avgPoint->apower = APcount ? (APtotal / APcount) : 0;
+    totalPoint->apower = APtotal;
+
     // and we're done
     dstale=false;
 }