[plotter] add xtransform

plotter.py

@@ -987,6 +987,7 @@ class Plotter(Aggregator, BaseProcessor):
         yunit=None,
         xunit_coeff=1.0,
         yunit_coeff=1.0,
+        xtransform=None,
         ytransform=None,
         xscale="linear",
         yscale="linear",
@@ -1093,9 +1094,17 @@ class Plotter(Aggregator, BaseProcessor):
         if isinstance(yerr, str):
             yerr = self.save.get_node(yerr).read()
 
+        # Apply transformations on x
+        if xtransform is not None:
+            x = xtransform(x)
+
         # Apply transformations on y
         if ytransform is not None:
             y = ytransform(y)
+            if yerr is not None:
+                self._log(
+                    "Errorbar may be meaning less when ytransform is used", "WARNING"
+                )
         if smooth > 0:
             y = gaussian_filter1d(y, sigma=smooth)
         if run is not None: