Adding support for base values going high to low in radixmath::interpolateToNewBaseValues

radixmath/interpolate.cc

@@ -164,20 +164,38 @@ std::vector<T> interpolateToOtherBaseValues(
   }
   radix_line("  Initial interpolation complete");
 
+  // Work out if the base array goes low to high or high to low
+  bool lowToHigh = true;
+  if (baseValues.front() < baseValues.back())
+  {
+    radix_line("  Base values go low to high");
+  }
+  else
+  {
+    lowToHigh = false;
+    radix_line("  Base values go high to low");
+  }
+
   // Iterate over the new base vector to calculate values at these positions
   radix_line("  Interpolating to new base values");
   for (size_t i = 0; i < newBaseValues.size(); ++i)
   {
     // Fill in values with a new base lower than the lowest original
-    if (newBaseValues[i] < baseValues.front())
+    if ((lowToHigh && newBaseValues[i] < baseValues.front()) ||
+        (!lowToHigh && newBaseValues[i] < baseValues.back()))
     {
-      radix_line("    Base value below range: filling with lowest");
+      radix_line("    Base value "
+                 << newBaseValues[i] << " below range " << baseValues.front()
+                 << "-" << baseValues.back() << ": filling with lowest");
       finalInterpolatedValues[i] = initialInterpolatedValues.front();
     }
     // Fill in values with a new base higher than the highest original
-    else if (newBaseValues[i] > baseValues.back())
+    else if ((lowToHigh && newBaseValues[i] > baseValues.back()) ||
+             (!lowToHigh && newBaseValues[i] > baseValues.front()))
     {
-      radix_line("    Base value above range: filling with highest");
+      radix_line("    Base value "
+                 << newBaseValues[i] << " above range " << baseValues.front()
+                 << "-" << baseValues.back() << ": filling with highest");
       finalInterpolatedValues[i] = initialInterpolatedValues.back();
     }
     // Fill in central values

radixmath/interpolate.hh

@@ -12,7 +12,7 @@
 namespace radix
 {
 template <typename T>
-extern std::vector<T> RADIX_PUBLIC interpolateValues(
+std::vector<T> RADIX_PUBLIC interpolateValues(
     const std::vector<T> &baseValues, const std::vector<T> &valuesToInterpolate,
     const bool circular = false, const T missingValue = -9999.f);