I've done this sort of thing before. I used two sliders to control the section of the plot I want extract. There were two lines, one on each end of the section. The sliders each used line() to draw a vertical line at the location of their end of the section. So set up two sliders, one called sldLeftEdge, and one called sldRightEdge. In the callback for those, you move the lines indicating the starting and ending location. You can also cut the data right then, or you can have a separate button that plots the data between the left and right edge. If you need example code, see below.
% --- Executes on slider movement.
function sldLeftEdge_Callback(hObject, eventdata, handles)
% hObject handle to sldLeftEdge (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Hints: get(hObject,'Value') returns position of slider
% get(hObject,'Min') and get(hObject,'Max') to determine range of slider
sliderValue = get(handles.sldLeftEdge, 'Value');
toolTipText = sprintf('Slider value = %.1f', sliderValue);
set(handles.sldLeftEdge, 'TooltipString', toolTipText);
set(handles.txtLeftEdge, 'String', toolTipText);
handles = SliderCallback(handles);
guidata(hObject, handles);
return;
%=====================================================================
function handles = SliderCallback(handles)
% Disable all controls. Re-enable later with GroupSet
WasEnabled = DisableAllControls_Pointer(handles, 'watch');
% Get the slider value.
sliderLeftEdgeValue = int32(round(get(handles.sldLeftEdge, 'Value')));
sliderRightEdgeValue = int32(round(get(handles.sldRightEdge, 'Value')));
% Update the label above the sliders.
newLabelLeft = sprintf('Left Edge is at %d', sliderLeftEdgeValue);
set(handles.txtLeftEdge, 'string', newLabelLeft);
newLabelRight = sprintf('Right Edge is at %d', sliderRightEdgeValue);
set(handles.txtRightEdge, 'string', newLabelRight);
% Move the vertical lines to show the new positions.
PlaceBothEdgesOnPlot(handles, sliderLeftEdgeValue, sliderRightEdgeValue);
MakeMeasurements(sliderLeftEdgeValue, sliderRightEdgeValue);
% Display the results in the info box.
% handles = DisplayResults(handles, resultsArray);
% Re-enable all those controls we disabled with DisableAllControls_Pointer
GroupSet(handles, WasEnabled, 'Enable', 'on');
set(handles.figMainWindow, 'Pointer', 'arrow');
return;
%=====================================================================
% Shows vertical lines going up from the X axis to the curve on the plot.
function PlaceBothEdgesOnPlot(handles, x1, x2)
% If the plot is visible, plot the line.
persistent handlesToVerticalBars;
if get(handles.axesPlot, 'visible')
axes(handles.axesPlot); % makes existing axes handles.axesPlot the current axes.
maxYValue = max(ylim);
% Make sure x location is in the valid range along the horizontal X axis.
XRange = get(handles.axesPlot, 'XLim');
maxXValue = XRange(2);
if x1 > maxXValue
x1 = maxXValue;
end
if x2 > maxXValue
x2 = maxXValue;
end
% Erase the old lines.
if ~isempty(handlesToVerticalBars)
try
delete(handlesToVerticalBars);
catch ME
end
end
% Draw vertical lines at the slope start and end locations.
hold on;
handlesToVerticalBars(1) = PlaceVerticalBarOnPlot(handles, x1, 'g');
handlesToVerticalBars(2) = PlaceVerticalBarOnPlot(handles, x2, 'r');
% Draw lines from curve at left edge to curve at right edge.
% handlesToVerticalBars(3) = line([x1 x2], [profileArray(x1) profileArray(x2)], 'Color', 'b');
hold off;
end
return; % End of PlaceBothEdgesOnPlot
%=====================================================================
% Shows vertical lines going up from the X axis on the plot.
function lineHandle = PlaceVerticalBarOnPlot(handles, x, lineColor)
% If the plot is visible, plot the line.
if get(handles.axesPlot, 'visible')
axes(handles.axesPlot); % makes existing axes handles.axesPlot the current axes.
% Make sure x location is in the valid range along the horizontal X axis.
XRange = get(handles.axesPlot, 'XLim');
maxXValue = XRange(2);
if x > maxXValue
x = maxXValue;
end
% Erase the old line.
%hOldBar=findobj('type', 'hggroup');
%delete(hOldBar);
% Draw a vertical line at the X location.
hold on;
yLimits = ylim;
lineHandle = line([x x], [yLimits(1) yLimits(2)], 'Color', lineColor);
hold off;
end
return; % End of PlaceVerticalBarOnPlot
