Fix missing implementation for .PLOT

Author: marcin-golebiowski

src/SpiceSharpParser/ModelReaders/Netlist/Spice/Readers/Controls/PlotControl.cs

@@ -155,15 +155,33 @@ private void AddPlotToResultIfValid(string plotImage, IReadingContext context, X
             }
             else
             {
-                context.Result.ValidationResult.AddError(ValidationEntrySource.Reader,  $"{plotImage} is not valid for: {simulation.Name}");
+                context.Result.ValidationResult.AddError(ValidationEntrySource.Reader, $"{plotImage} is not valid for: {simulation.Name}");
             }
         }
 
         private void CreatePointForSeries(ISimulationWithEvents simulation, IReadingContext context, object eventArgs, List<Export> exports, List<Series> series)
         {
             double x = 0;
 
-            //TODO
+            if (simulation is Transient transient)
+            {
+                x = transient.Time;
+            }
+
+            if (simulation is AC frequency)
+            {
+                x = frequency.Frequency;
+            }
+
+            if (simulation is Noise noise)
+            {
+                x = noise.Frequency;
+            }
+
+            if (simulation is DC dc)
+            {
+                x = dc.GetCurrentSweepValue().FirstOrDefault();
+            }
 
             for (var i = 0; i < exports.Count; i++)
             {