PPM display partially implemented

src/data/DamarisFFT.py

@@ -225,3 +225,13 @@ class DamarisFFT:
         self.y[ 0 ] = numpy.sqrt( self.y[ 0 ] ** 2 + self.y[ 1 ] ** 2 )
         self.y[ 1 ] *= 0  # self.y[0].copy()
         return self
+
+    def ppm(self, f_ref):
+        """
+        Return result scaled to PPM compared to f_ref
+
+        :param f_ref: larmor frequency in Hz
+        :return:
+        """
+        self.y /= f_ref*1e6
+        return self

src/gui/damaris.glade

@@ -596,7 +596,8 @@ log10</property>
                                 <property name="focus_on_click">False</property>
                                 <property name="items" translatable="yes">lin
 log
-log10</property>
+log10
+ppm</property>
                                 <signal name="changed" handler="on_display_x_scaling_combobox_changed"/>
                               </widget>
                               <packing>
@@ -1471,7 +1472,7 @@ Homepage http://www.fkp.physik.tu-darmstadt.de/damaris/
 
 Python frontend written by Christopher Schmitt, Achim Gädke, Markus Rosenstihl and Christian Tacke
 Backends written by Achim Gädke, Markus Rosenstihl, Christian Tacke, tested by Holger Stork
-The drivers included in the backend may use propietary interfaces.
+The drivers included in the backend may use proprietary interfaces.
 The source code distribution may include commercial third party's code,
 which is specially marked and not covered by this license.