diff --git a/applications/lazstats/source/forms/analysis/descriptive/resistancelineunit.pas b/applications/lazstats/source/forms/analysis/descriptive/resistancelineunit.pas
index 4f6add797..bbb59ca8b 100644
--- a/applications/lazstats/source/forms/analysis/descriptive/resistancelineunit.pas
+++ b/applications/lazstats/source/forms/analysis/descriptive/resistancelineunit.pas
@@ -11,7 +11,7 @@ interface
 
 uses
   Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs,
-  StdCtrls, ExtCtrls, Buttons, Printers, ComCtrls,
+  StdCtrls, ExtCtrls, Buttons, Printers, ComCtrls, Grids,
   MainUnit, Globals, DataProcs, DictionaryUnit,
   MathUnit, BasicStatsReportAndChartFormUnit;
 
@@ -57,10 +57,14 @@ type
     procedure PlotXY(const XPoints, YPoints: DblDyneVec;
       ARegressionResults: TBivariateRegressionResults);
 
+    function PrepareData(ADataGrid: TStringGrid;
+      out xCol, ycol: Integer; out XData, YData: DblDyneVec;
+      out ColNoSelected: IntDyneVec): Boolean;
+
     procedure ResidualsToGrid(xCol, yCol: Integer;
       const AColNoSelected: IntDyneVec; Slope, Intercept: Double);
 
-    procedure ResistantLineAnalysis(const xyPoints: DblDyneMat;
+    procedure ResistantLineAnalysis(const XData, YData: DblDyneVec;
       out XMedians, yMedians: DblDyneVec; out GrpSize: IntDyneVec);
 
     procedure WriteMedianReport(AReport: TStrings;
@@ -87,7 +91,7 @@ implementation
 {$R *.lfm}
 
 uses
-  Math, Grids,
+  Math,
   TATypes, TAChartUtils, TAChartAxisUtils, TALegend, TASources, TACustomSeries,
   ChartFrameUnit, Utils, GridProcs;
 
@@ -136,14 +140,14 @@ end;
 
 procedure TResistanceLineForm.Compute;
 var
-  xyPoints: DblDyneMat = nil;   // 1st index: x or y, 2nd index: data index
+  xValues: DblDyneVec = nil;
+  yValues: DblDyneVec = nil;
   xMedians: DblDyneVec = nil;
   yMedians: DblDyneVec = nil;
   colNoSelected : IntDyneVec = nil;
   grpSize: IntDyneVec = nil;
   xCol, yCol: Integer;
   regressionRes: TBivariateRegressionResults;
-  N: Integer;
   confBand: Double;
   slope1, slope2, slopeRL: Double;
   c1, c2, c3, c: Double;
@@ -152,48 +156,19 @@ var
 begin
   dataGrid := OS3MainFrm.DataGrid;
 
-  xCol := GetVariableIndex(dataGrid, XEdit.Text);
-  yCol := GetVariableIndex(dataGrid, YEdit.Text);
-  if xCol = -1 then
-  begin
-    ErrorMsg('X variable not specified or not found.');
-    exit;
-  end;
-  if yCol = -1 then
-  begin
-    ErrorMsg('Y variable not specified or not found.');
-    exit;
-  end;
-
-  SetLength(colNoSelected, 2);
-  colNoSelected[0] := xCol;
-  colNoSelected[1] := yCol;
-
   // Get values from the grid
-  SetLength(xyPoints, 2);
-  xyPoints[0] := CollectValues(dataGrid, xCol, colNoSelected);
-  xyPoints[1] := CollectValues(dataGrid, ycol, colNoSelected);
-  N := Length(xyPoints[0]);
-  if N < 3 then
-  begin
-    ErrorMsg('At least three data points required.');
+  if not PrepareData(dataGrid, xCol, yCol, xValues, yvalues, colNoSelected) then
     exit;
-  end;
-  if N <> Length(xyPoints[1]) then
-  begin
-    ErrorMsg('Equal count of cases required for x and y variables.');
-    exit;
-  end;
 
   // Sort on the x values
-  SortOnX(xyPoints[0], xyPoints[1]);
+  SortOnX(xValues, yValues);
 
   // Calculate bivariate regression
   confBand := StrToFloat(ConfEdit.Text) / 100;
-  Calc_BivariateRegression(xyPoints[0], xyPoints[1], confBand, regressionRes);
+  Calc_BivariateRegression(xValues, yValues, confBand, regressionRes);
 
   // Do the resistant line analysis
-  ResistantLineAnalysis(xyPoints, xMedians, yMedians, grpSize);
+  ResistantLineAnalysis(xValues, yValues, xMedians, yMedians, grpSize);
 
   slope1 := (yMedians[1] - yMedians[0]) / (xMedians[1] - xMedians[0]);
   slope2 := (yMedians[2] - yMedians[1]) / (xMedians[2] - xMedians[1]);
@@ -230,10 +205,10 @@ begin
 
   // Plot results in ChartFrame
   if PlotPointsChk.Checked then
-    PlotXY(xyPoints[0], xyPoints[1], regressionRes);
+    PlotXY(xValues, yValues, regressionRes);
 
   if PlotMediansChk.Checked then
-    PlotMedians(XMedians, YMedians, slopeRL, c);
+    PlotMedians(xMedians, yMedians, slopeRL, c);
 end;
 
 
@@ -356,6 +331,54 @@ begin
 end;
 
 
+function TResistanceLineForm.PrepareData(ADataGrid: TStringGrid;
+  out xCol, ycol: Integer; out XData, YData: DblDyneVec;
+  out ColNoSelected: IntDyneVec): Boolean;
+var
+  N: Integer;
+begin
+  Result := false;
+
+  ColNoSelected := nil;
+  XData := nil;
+  YData := nil;
+
+  xCol := GetVariableIndex(ADataGrid, XEdit.Text);
+  yCol := GetVariableIndex(ADataGrid, YEdit.Text);
+  if xCol = -1 then
+  begin
+    ErrorMsg('X variable not specified or not found.');
+    exit;
+  end;
+
+  if yCol = -1 then
+  begin
+    ErrorMsg('Y variable not specified or not found.');
+    exit;
+  end;
+
+  SetLength(ColNoSelected, 2);
+  ColNoSelected[0] := xCol;
+  ColNoSelected[1] := yCol;
+
+  XData := CollectValues(ADataGrid, xCol, colNoSelected);
+  YData := CollectValues(ADataGrid, ycol, colNoSelected);
+  N := Length(XData);
+  if N < 3 then
+  begin
+    ErrorMsg('At least three data points required.');
+    exit;
+  end;
+  if N <> Length(YData) then
+  begin
+    ErrorMsg('Equal count of cases required for x and y variables.');
+    exit;
+  end;
+
+  Result := true;
+end;
+
+
 procedure TResistanceLineForm.Reset;
 var
   i: integer;
@@ -421,14 +444,14 @@ begin
 end;
 
 { Do the resistant line analysis }
-procedure TResistanceLineForm.ResistantLineAnalysis(const xyPoints: DblDyneMat;
+procedure TResistanceLineForm.ResistantLineAnalysis(const XData, YData: DblDyneVec;
   out XMedians, yMedians: DblDyneVec; out GrpSize: IntDyneVec);
 var
   i, N, offs: Integer;
   xVector: DblDyneVec = nil;
   yVector: DblDyneVec = nil;
 begin
-  N := Length(xyPoints[0]);
+  N := Length(XData);
 
   GrpSize := nil;
   XMedians := nil;
@@ -453,8 +476,8 @@ begin
   offs := 0;
   for i := 0 to GrpSize[1] - 1 do
   begin
-    xVector[i] := xyPoints[0, i + offs];
-    yVector[i] := xyPoints[1, i + offs];
+    xVector[i] := XData[i + offs];
+    yVector[i] := YData[i + offs];
   end;
   xMedians[0] := Calc_Median(xVector);
   yMedians[0] := Calc_Median(yVector);
@@ -465,8 +488,8 @@ begin
   offs := GrpSize[0];
   for i := 0 to GrpSize[1] - 1 do
   begin
-    xVector[i] := xyPoints[0, i + offs];
-    yVector[i] := xyPoints[1, i + offs];
+    xVector[i] := XData[i + offs];
+    yVector[i] := YData[i + offs];
   end;
   xMedians[1] := Calc_Median(xVector);
   yMedians[1] := Calc_Median(yVector);
@@ -477,8 +500,8 @@ begin
   offs := GrpSize[0] + GrpSize[1];
   for i := 0 to GrpSize[2] - 1 do
   begin
-    xVector[i] := xyPoints[0, i + offs];
-    yVector[i] := xyPoints[1, i + offs];
+    xVector[i] := XData[i + offs];
+    yVector[i] := YData[i + offs];
   end;
   xMedians[2] := Calc_Median(xVector);
   yMedians[2] := Calc_Median(yVector);