Index: /branches/eam_rel9_p0/psModules/src/objects/Makefile.am
===================================================================
--- /branches/eam_rel9_p0/psModules/src/objects/Makefile.am	(revision 5980)
+++ /branches/eam_rel9_p0/psModules/src/objects/Makefile.am	(revision 5981)
@@ -8,4 +8,5 @@
     pmPSFtry.c \
     pmModelGroup.c \
+    pmGrowthCurve.c \
     psEllipse.c
 
@@ -22,3 +23,4 @@
     pmPSFtry.h \
     pmModelGroup.h \
+    pmGrowthCurve.h \
     psEllipse.h
Index: /branches/eam_rel9_p0/psModules/src/objects/pmGrowthCurve.c
===================================================================
--- /branches/eam_rel9_p0/psModules/src/objects/pmGrowthCurve.c	(revision 5981)
+++ /branches/eam_rel9_p0/psModules/src/objects/pmGrowthCurve.c	(revision 5981)
@@ -0,0 +1,116 @@
+#include <pslib.h>
+# include "pmGrowthCurve.h"
+
+static void pmGrowthCurveFree (pmGrowthCurve *growth)
+{
+
+    if (growth == NULL)
+        return;
+
+    psFree (growth->radius);
+    psFree (growth->apMag);
+    return;
+}
+
+pmGrowthCurve *pmGrowthCurveAlloc (psF32 minRadius, psF32 maxRadius, psF32 dRadius)
+{
+
+    pmGrowthCurve *growth = psAlloc (sizeof(pmGrowthCurve));
+    psMemSetDeallocator(growth, (psFreeFunc) pmGrowthCurveFree);
+
+    growth->radius = psVectorCreate (NULL, minRadius, maxRadius, dRadius, PS_TYPE_F32);
+    growth->apMag  = psVectorAlloc (growth->radius->n, PS_TYPE_F32);
+
+    // XXX may want to extend this to allow for a different refRadius;
+    growth->refRadius = maxRadius;
+    growth->maxRadius = maxRadius;
+    growth->apLoss = 0.0;
+    growth->fitMag = 0.0;
+    return growth;
+}
+
+psF32 pmGrowthCurveCorrect (pmGrowthCurve *growth, psF32 radius)
+{
+
+    float apRad = psVectorInterpolate (growth->radius, growth->apMag, radius);
+    float apCor = growth->apRef - apRad;
+    return apCor;
+}
+
+// return the last entry below or first entry above key value
+int psVectorBracket (psVector *index, psF32 key, bool above)
+{
+
+    int N;
+    int Nlo = 0;
+    int Nhi = index->n;
+
+    if (above) {
+        while (Nhi - Nlo > 10) {
+            N = 0.5*(Nlo + Nhi);
+            if (index->data.F32[N] > key) {
+                Nhi = N;
+            } else {
+                Nlo = N - 1;
+            }
+        }
+        // at this point, index[Nhi] > key >= index[Nlo]
+        N = Nlo;
+        while ((index->data.F32[N] <= key) && (N < Nhi)) {
+            N++;
+        }
+        return (N);
+    }
+    while (Nhi - Nlo > 10) {
+        N = 0.5*(Nlo + Nhi);
+        if (index->data.F32[N] < key) {
+            Nlo = N;
+        } else {
+            Nhi = N + 1;
+        }
+    }
+    // at this point, index[Nhi] >= key > index[Nlo]
+    N = Nhi;
+    while ((index->data.F32[N] >= key) && (N > Nlo)) {
+        N--;
+    }
+    return (N);
+}
+
+// search for the bins bounding key in index, interpolate the corresponding values
+psF32 psVectorInterpolate (psVector *index, psVector *value, psF32 key)
+{
+
+    int n0 = 0;
+    int n1 = 0;
+
+    // extrapolate at ends
+    if (key < index->data.F32[0]) {
+        n0 = 0;
+        n1 = 1;
+    }
+
+    // extrapolate at ends
+    if (key > index->data.F32[index->n-1]) {
+        n0 = index->n-2;
+        n1 = index->n-1;
+    }
+
+    if (n1 == 0) {
+        int n0 = psVectorBracket (index, key, FALSE);
+        n1 = n0 + 1;
+    }
+
+    if (n0 == index->n-1) {
+        n1 = n0;
+        n0 = n1 - 1;
+    }
+
+    float dy = value->data.F32[n1] - value->data.F32[n0];
+    float dx = index->data.F32[n1] - index->data.F32[n0];
+    float dX = key - index->data.F32[n0];
+    float dY = dX * (dy/dx);
+    float result = value->data.F32[n0] + dY;
+    return result;
+}
+
Index: /branches/eam_rel9_p0/psModules/src/objects/pmGrowthCurve.h
===================================================================
--- /branches/eam_rel9_p0/psModules/src/objects/pmGrowthCurve.h	(revision 5981)
+++ /branches/eam_rel9_p0/psModules/src/objects/pmGrowthCurve.h	(revision 5981)
@@ -0,0 +1,21 @@
+# ifndef PM_GROWTH_CURVE_H
+# define PM_GROWTH_CURVE_H
+
+typedef struct
+{
+    psVector *radius;
+    psVector *apMag;
+    psF32 refRadius;
+    psF32 maxRadius;
+    psF32 fitMag;
+    psF32 apRef;   // apMag[refRadius]
+    psF32 apLoss;  // fitMag - apRef
+}
+pmGrowthCurve;
+
+pmGrowthCurve *pmGrowthCurveAlloc (psF32 minRadius, psF32 maxRadius, psF32 dRadius);
+int psVectorBracket (psVector *index, psF32 key, bool above);
+psF32 psVectorInterpolate (psVector *index, psVector *value, psF32 key);
+psF32 pmGrowthCurveCorrect (pmGrowthCurve *growth, psF32 radius);
+
+# endif /* PM_GROWTH_CURVE_H */