final nonmonotonic handling

src/ramanchada2/protocols/calibration/xcalibration.py

@@ -78,13 +78,20 @@ def process(
 
                 elif isinstance(self.model, CustomCubicSplineInterpolator):
                     new_spe.x = self.model(new_spe.x)
-                if not np.all(np.diff(new_spe.x) > 0):
-                    if self.nonmonotonic == "nan":
+
+                if np.any(np.diff(new_spe.x[np.isfinite(new_spe.x)]) <= 0):                    
+                    if self.nonmonotonic == "error":
+                        raise ValueError("Non-monotonic values detected (mode={})",self.nonmonotonic)
+                    elif self.nonmonotonic == "nan":
+                        # this is a patch, mostly intended at extrapolation 
                         new_spe.x = np.asarray(new_spe.x, dtype=float)
                         is_nonmonotonic = np.diff(new_spe.x, prepend=new_spe.x[0]) <= 0
                         new_spe.x[is_nonmonotonic] = np.nan
-                    elif self.nonmonotonic == "error":
-                        raise ValueError("Non-monotonic values detected")
+                        # we don't necessary ensure monotonicity by setting nans
+                        if np.any(np.diff(new_spe.x[np.isfinite(new_spe.x)]) <= 0):
+                            raise ValueError("Non-monotonic values detected (mode={})",self.nonmonotonic)
+
+                    # else ignore
 
         if convert_back:
             return self.convert_units(new_spe, self.model_units, spe_units)