If the plot is on it's own figure, you can get the figure handle first: hFig1 = figure; plot(1:9, 'b-'); % more code to do stuff on other figures; % Now switch back to the first figure: figure(hFig1); If you're on the same figure, you can use the axes handle to switch focus to the axes you want: axes(handles.axes1); plot(1:9, 'b-'); % Switch focus to second plot on the same figure. axes(handles.axes2); plot(sin(0:0.1:2*pi), 'b-'); % Switch back to axes #1 axes(handles.axes1); plot(2:25, 'r-');

People seem not to recognize this. Not sure why, but it seems a common misperception. A level set is the set of all points where the function z(x1,x2) is constant, at some given value. In this case, that value is z(x1,x2)==1. So you want to do a contour plot! The obvious solution is to try ezcontour. But if you did, you will be disapponted. Why? Because ezcontour does not allow you to specify the contour level of interest. Here, that is z(x1,x2) = 1. (Actually, it looks like ezcontour is now being deprecated, to be replaced eventually by fcontour. Sadly, they still have not obviously given us the ability to plot only ONE desired contour line with fcontour. IMHO, that would be a mistake. HAPPILY, they did give us that capability! It is just not documented as well as I would have liked.) Instead, the classic solution in MATLAB is to use contour. Contour works on an array of values. So in the classical solution, you would first use meshgrid to generate a grid over x1 and x2. Then evaluate the function at each grid point in the arrays of x1 and x2, representing points in the (x1,x2) plane. Only then call contour, telling it to use a SPECIFIC contour level, here z==1. So, lets instead try using a simpler solution in MATLAB, thus fcontour. Create a function of two variables. Simplest is to learn about function handles. Don't forget to use the correct operators, that will allow vectorized operations between arrays of x1 and x2. Here that means you need to use the .^ and .* operators. zfun = @(x1,x2) x1.^2 + x2.^2 - x1.*x2; zhandle = fcontour(zfun) zhandle = FunctionContour with properties: Function: @(x1,x2)x1.^2+x2.^2-x1.*x2 LineColor: 'flat' LineStyle: '-' LineWidth: 0.5000 Fill: 'off' LevelList: [10 20 30 40 50 60 70] Show all properties So I did a contour plot. So what? Where is the contour that indicates where z(x1,x2)==1? Look carefully at the properties we see there. We find LevelList! Will that help? zhandle.LevelList = 1; xlabel x1 ylabel x2 title(func2str(zfun)) grid on zhandle.YRange = [-2,2]; zhandle.XRange = [-2,2]; axis equal That looks reasonable now. Anyway, not difficult. It took a few lines of code to make the picture as pretty as I might like, but then I tend to be a perfectionist. It does get into some of the newer toys to be found in MATLAB, which is why I answered this question in some depth.

The plot function plots lines between two points. You appear to be plotting points, so you need to plot markers. Try this: for v = 5:20 for d = 20:120 w = (0.25*pi*(d.^2)*0.5*(v.^2)); plot(v,w,'.') hold on end end Experiment to get the result you want.

figure;
ah = axes;
hold(ah,'on');  
%Axes must have hold on or lh(1) will become invalid after lh(2) is created
lh(1) = plot(ah,[1 2 3],[1 2 3],'r','visible','off');
lh(2) = plot(ah,[1 2 3],[3 2 1],'b','visible','off');

This will turn on Line 1 (red)

set(lh(1),'visible','on');set(lh(2),'visible','off')

This will turn on Line 2 (blue)

set(lh(1),'visible','off');set(lh(2),'visible','on')

In your GUI you will need some kind of callback to cycle the visible on/off state off all your line handles. Note: If these are very large datasets and you have lots of lines it could eat up a bunch of memory.