Plotting contour lines at specific value
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I have two functions f1 and f2 defined as follows:
f1(x) = x_1^2 + x_2^2 - 4
f2(x) = 5(x_1 - 1)^2 - x_2 - 3
where x = (x_1,x_2)^T.
Now I want to plot the contour lines of these functions at value 0, that is, I want to plot the functions
x_1^2 + x_2^2 - 4 = 0
5(x_1 - 1)^2 - x_2 - 3 = 0
I tried using contourplot, but no luck there. Is there a smarter way, for example using Linspace?
采纳的回答
Matt Fig
2011-3-24
Please re-paste your code and use the code format button so we can read it. I see a bunch of ? marks in the code.
When using the CONTOUR function, you can provide an argument which tells the function where to draw the contours.
Here is a way to get a surface and contours in one plot:
[x_1,x_2] = meshgrid(-10:.1:10,-10:.1:10);
f1 = @(x_1,x_2) x_1.^2 + x_2.^2 - 4;
f2 = @(x_1,x_2) 5*(x_1 - 1).^2 - x_2 - 3;
subplot(2,1,1)
surfc(x_1,x_2,f1(x_1,x_2))
subplot(2,1,2)
surfc(x_1,x_2,f2(x_1,x_2))
To get just the surface, use the SURF function.
6 个评论
David
2011-3-24
Matt Fig
2011-3-24
From the documentation:
CONTOUR(Z,V) and CONTOUR(X,Y,Z,V) draw LENGTH(V) contour lines
at the values specified in vector V. Use CONTOUR(Z,[v v]) or
CONTOUR(X,Y,Z,[v v]) to compute a single contour at the level v.
David
2011-3-24
Matt Fig
2011-3-24
See my answer above.
Mohammad Sohail
2017-5-30
@David try this
syms x y
ezplot(x^2+y^2-4)
Avinash Kumar
2019-4-9
thanks
更多回答（1 个）
kanekal kullayappa
2014-2-24
0 个投票
hello sir, I need the function to obtain the plots in the joint tdoa and aoa location algorithm http://www.jseepub.com/EN/article/downloadArticleFile.do?attachType=PDF&id=11834.
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