Distinguishing between two surfaces

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A
A 2014-3-21
评论： Image Analyst 2014-3-22
Hi guys,
I have a simple question. I want to distinguish between two surfaces with x, y, and z values. The equations resemble like the ones here:
z = x + y; z = 2x + y;
I basically want to find out when z is different with the same values for x and y. I then want to be able to graph this 'difference'. Is it a simple thing to do? Is it as simple as subtracting the two equations?
If this is possible, then is it possible to do something similar with 3 or more surfaces with similar equations? I want to find x and y values where z is different for all equations.
I hope this makes sense.
Thank you

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回答（2 个）

Joseph Cheng
Joseph Cheng 2014-3-21
I would first call the two z something different that way you don't override the other z. Yes a simple subtraction would be something you could do and then you can use the surf(x,y,z1-z2) to show the difference. to find the the points that are different for the same x and y values, the find() function for when z1-z2~=0 (z1 subtract z2 does not equal 0) will give you the index of values not equal zero. when you introduce 3+ surfaces you can use the same find but you'll have to do some round robin comparison scheme and display it.
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A
A 2014-3-22
Thanks for your response. I will try your suggestion.
What do you mean by round robin stuff?
Thanks
Image Analyst
Image Analyst 2014-3-22
He means generate the 2 z's for every possible x,y coordinate. If not in a nice evenly spaces matrix (which is probably preferable), then at least such that z1 and z2 have values for the same pairs of (x,y) coordinates.

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A
A 2014-3-22
  1 个评论
Star Strider
Star Strider 2014-3-22
编辑：Star Strider 2014-3-22
‘ C = setdiff(A,B) returns the data in A that is not in B. ’
The setdiff function looks for the numbers that two arrays do not share. It will not do point-by-point comparisons.
I believe Joseph meant ‘round robin comparison scheme’ to be (z1 - z2), (z3 - z1), (z3 - z2), etc. in the event you have more than two surfaces you want to compare. You would probably have to plot the (z1 - z2), (z3 - z1), (z3 - z2) surfaces each in a different plot.

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