diff --git a/android-app/src/main/java/org/solovyev/android/calculator/plot/CalculatorPlotFunctionSettingsActivity.java b/android-app/src/main/java/org/solovyev/android/calculator/plot/CalculatorPlotFunctionSettingsActivity.java
index dfbdeee3..ad2dc0e3 100644
--- a/android-app/src/main/java/org/solovyev/android/calculator/plot/CalculatorPlotFunctionSettingsActivity.java
+++ b/android-app/src/main/java/org/solovyev/android/calculator/plot/CalculatorPlotFunctionSettingsActivity.java
@@ -97,7 +97,8 @@ public class CalculatorPlotFunctionSettingsActivity extends SherlockFragmentActi
 						final PlotLineColor newPlotLineColor = PlotLineColor.values()[position];
 						int newLineColor = newPlotLineColor.getColor();
 						if ( newLineColor != plotFunction.getPlotLineDef().getLineColor() ) {
-							final PlotFunction newPlotFunction = new PlotFunction(plotFunction.getXyFunction(), PlotLineDef.changeLineColor(plotFunction.getPlotLineDef(), newLineColor));
+							final PlotLineDef newPlotLineDef = PlotLineDef.changeLineColor(plotFunction.getPlotLineDef(), newLineColor);
+							final PlotFunction newPlotFunction = PlotFunction.changePlotLineDef(plotFunction, newPlotLineDef);
 							if(plotter.updateFunction(newPlotFunction)) {
 								plotFunction = newPlotFunction;
 							}
@@ -115,7 +116,8 @@ public class CalculatorPlotFunctionSettingsActivity extends SherlockFragmentActi
 					public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
 						final PlotLineColorType newPlotLineColorType = PlotLineColorType.values()[position];
 						if ( newPlotLineColorType != plotFunction.getPlotLineDef().getLineColorType() ) {
-							final PlotFunction newPlotFunction = new PlotFunction(plotFunction.getXyFunction(), PlotLineDef.changeLineColorType(plotFunction.getPlotLineDef(), newPlotLineColorType));
+							final PlotLineDef newPlotLineDef = PlotLineDef.changeLineColorType(plotFunction.getPlotLineDef(), newPlotLineColorType);
+							final PlotFunction newPlotFunction = PlotFunction.changePlotLineDef(plotFunction, newPlotLineDef);
 							if(plotter.updateFunction(newPlotFunction)) {
 								plotFunction = newPlotFunction;
 							}
@@ -133,7 +135,10 @@ public class CalculatorPlotFunctionSettingsActivity extends SherlockFragmentActi
 					public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
 						final PlotLineStyle newPlotLineStyle = PlotLineStyle.values()[position];
 						if ( newPlotLineStyle != plotFunction.getPlotLineDef().getLineStyle() ) {
-							final PlotFunction newPlotFunction = new PlotFunction(plotFunction.getXyFunction(), PlotLineDef.changeLineStyle(plotFunction.getPlotLineDef(), newPlotLineStyle));
+
+							final PlotLineDef newPlotLineDef = PlotLineDef.changeLineStyle(plotFunction.getPlotLineDef(), newPlotLineStyle);
+							final PlotFunction newPlotFunction = PlotFunction.changePlotLineDef(plotFunction, newPlotLineDef);
+
 							if(plotter.updateFunction(newPlotFunction)) {
 								plotFunction = newPlotFunction;
 							}
diff --git a/core/src/main/java/org/solovyev/android/calculator/plot/PlotFunction.java b/core/src/main/java/org/solovyev/android/calculator/plot/PlotFunction.java
index 25fab115..1b462633 100644
--- a/core/src/main/java/org/solovyev/android/calculator/plot/PlotFunction.java
+++ b/core/src/main/java/org/solovyev/android/calculator/plot/PlotFunction.java
@@ -13,7 +13,7 @@ public class PlotFunction {
     private XyFunction xyFunction;
 
     @NotNull
-    private PlotLineDef mPlotLineDef;
+    private PlotLineDef plotLineDef;
 
     private boolean pinned = false;
 
@@ -21,26 +21,34 @@ public class PlotFunction {
 
     public PlotFunction(@NotNull XyFunction xyFunction) {
         this.xyFunction = xyFunction;
-        this.mPlotLineDef = PlotLineDef.newDefaultInstance();
+        this.plotLineDef = PlotLineDef.newDefaultInstance();
     }
 
     public PlotFunction(@NotNull XyFunction xyFunction,
                         @NotNull PlotLineDef plotLineDef) {
         this.xyFunction = xyFunction;
-        this.mPlotLineDef = plotLineDef;
+        this.plotLineDef = plotLineDef;
     }
 
     @NotNull
     private PlotFunction copy() {
         final PlotFunction copy = new PlotFunction(this.xyFunction);
 
-        copy.mPlotLineDef = this.mPlotLineDef;
+        copy.plotLineDef = this.plotLineDef;
         copy.pinned = this.pinned;
         copy.visible = this.visible;
 
         return copy;
     }
 
+	@NotNull
+	public static PlotFunction changePlotLineDef(@NotNull PlotFunction that, @NotNull PlotLineDef newPlotLineDef) {
+		final PlotFunction copy = that.copy();
+		copy.plotLineDef = newPlotLineDef;
+		return copy;
+	}
+
+	@NotNull
     public static PlotFunction pin(@NotNull PlotFunction that) {
         return togglePinned(that, true);
     }
@@ -81,7 +89,7 @@ public class PlotFunction {
 
     @NotNull
     public PlotLineDef getPlotLineDef() {
-        return mPlotLineDef;
+        return plotLineDef;
     }
 
     public boolean isPinned() {