How to create a graph with X, Y + Contour Axes.

Hello, I need some guidance for creating a very similar chart shown below in the link.

http://i146.photobucket.com/albums/r268/krankxx/Untitled-1-7.jpg

For each axis, including the contoured one, I also have some data between 0-1 (actally % values) of corresponding type and I am supposed to show them in a single chart. I am not sure about how to combine those different values into one. If someone can offer some guidance with key functions, I would be greatly faithful.

Thanks in advance.

Answer 1

[the cyclist]

Here is a simple example, which I hope you can bend to your needs. I adapted it from the documentation here: http://www.mathworks.com/help/techdoc/ref/contour.html. I think it illustrates most of what you want, including how to overlay multiple plots (with the hold command), adding labels to the contours, etc. There are help files for all the different functions I used, of course.

figure
hold on

[X,Y] = meshgrid(-2:.2:2,-2:.2:3);
Z = X.*exp(-X.^2-Y.^2);

[C,h] = contour(X,Y,Z);
set(h,'ShowText','on','TextStep',get(h,'LevelStep')*2)

addedRandomX = rand(1,20);
addedRandomY = rand(1,20);

plot(addedRandomX, 1+addedRandomY,'kx')
plot(-addedRandomX,1+addedRandomY,'ro')

[Al Onen]

Hello, I couldnt find time to work on this earlier, but I'm still stuck. It turned out to be the main function of contour lines is Z = (1/((1/(1-Y))+(1/X)-1)), and it's not applicable when X or Y are equal to 1 or 0, so that's why contour lines are between 0.1 and 0.9 on the linked chart and can't use Z as a single variable on code because of not fitting matrix dimensions with X and Y matrices. I also tried to plot contours individually, but failed. I'm not good at Matlab and definitely doing something wrong; so if you could spare few more moments to help, i would be more faithful :)

[the cyclist]

Can you post your code and explain in more detail what is wrong? Is the code producing an error, or just results that you don't expect?

[Al Onen]

Firstly I tried

figure

hold on

[X,Y] = meshgrid(-2:.2:2,-2:.2:3);

Z = (1/((1/(1-Y))+(1/X)-1));

[C,h] = contour(X,Y,Z);

...

But Matlab gave an Matrix dimensions error;

??? Error using ==> mldivide

Matrix dimensions must agree.

Error in ==> cont at 5

Z = (1/((1/(1-Y))+(1/X)-1));

I also tried to create a loop to bypass invalid intervals for Z (X and/or Y = 1 and 0), but couldn't manage to create proper codes.

Lastly, I created the mesh for X & Y for desired intervals, and try to implement curves of Z individually with fplot function, and but since my Z function is 2-variable dependent, I couldnt manage the run the code as well logically.

Just had a thought, Should I try plotting them with some differential equation approach?

Sorry for being a headache by the way :)

[the cyclist]

The reason you got the mldivide error when calculating Z is that you were using the syntax for matrix division, where you actually wanted element-by-element division.

Try this instead:

figure

hold on

[X,Y] = meshgrid(-2:.2:2,-2:.2:3);

Z = 1./((1./(1-Y))+(1./X)-1);

[C,h] = contour(X,Y,Z)

Notice that I added "./" in place of just "/". The dots are the syntax for element-by-element operations.

I'm not sure if the result is what you expect, but at least it executes.

[Al Onen]

Thank you so much. Indeed it works - I'm such a loser with Matlab. :) I have to keep the purpose of dots in mind. Now the answer is officially accepted.

Answer 2

[Al Onen]

Thank you, that will probably do the trick.