How can I plot a surface with changing constant?

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A
A 2014-4-17
编辑： A 2014-4-18
Hi guys,
I have a complex question. I want to graph the following equation as a surface. However, the constant A changes with a certain value of the y-axis:
Want to graph: z = M - 10x - 3.5y
Where
M = 5 + 3 for y < 10
M = 5 + 4 for 10 < y < 20
M = 5 + 5 for 20 < y < 30
Does this make sense? The value of the constant depends on the value of the y.
How can I approach this?
Thanks

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采纳的回答

Star Strider
Star Strider 2014-4-17
I suggest this as a possibility:
M = [3 4 5];
z = @(x,y) 5 + M(max(1,fix((y-30+0.1)/10)+3)) - 10.*x - 3.5.*y;
I tested the M-matrix addressing with this statement:
Mr = [y' max(1,(fix((y-30)/10)+3))' M(max(1,fix((y-30+0.1)/10)+3))']
The surface plot is an inclined plane.
  2 个评论
Star Strider
Star Strider 2014-4-17
编辑：Star Strider 2014-4-18
There are in the code I tested, both with the Mr test variable and with z(y) with a fixed x=15. I was expecting visible discontinuities in the surface plot with X and Y defined with meshgrid with x and y defined as [0:0.1:30], but when I looked for them in the 2D plot, they were there but barely visible.

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更多回答（1 个）

Walter Roberson
Walter Roberson 2014-4-17
[X, Y] = ndgrid(....);
Z = 5 - 10 * X - 3.5 * Y;
Z(10 < Y & Y < 20) = Z(10 < Y & Y < 20) + 4;
and so on.
Note: your M is not defined for Y = 10 exactly or Y = 20 exactly
  1 个评论
A
A 2014-4-18
编辑：A 2014-4-18
Thank you for the solutions to you both.
I'm uncertain which solution is the best one to use in my case?
I want to be able to graph this as a surface?
Thank you

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