How to include zero contour
显示 更早的评论
Hi,
In the .m file attached, I have a plot of a contour.
The plot for the contour is on line 111. Please how can I include the contour at imag(taumin)=0.
采纳的回答
Walter Roberson
2023-10-10
taumin is not complex, so imag(taumin) is zero everywhere. There is no contour to create.
You initialize
taumin=ones(nu,nxi);
which is not complex.
You set
taumin(i,j)=min(tausolR);
where
tausolR=imag(tausol_found);
You extract the imaginary component from tausol_found so the result is a strictly real number, and real numbers always have an all-zero imaginary component.
If the task is to include 0 in the level list then use
LL = union(0, min(min(taumin)):10000:max(max(taumin)));
contourf(U,Xi,taumin,LL);
Beware though, that min(min(taumin)) is -4.32538271227367e-07 and max(max(taumin)) is 1, so min(min(taumin)):10000:max(max(taumin)) is -4.32538271227367e-07:10000:1 which is just -4.32538271227367e-07
9 个评论
University
2023-10-10
University
2023-10-11
Walter Roberson
2023-10-11
Why does your code only produce a single taumin() value per inner loop, but plots everything for every iteration ?
Walter Roberson
2023-10-11
Extracting the data from the contour plot, I see that the maximum Z data for the plot is -2.61427978861032e-08 -- so there is no zero to be plotted.
University
2023-10-11
编辑：University
2023-10-11
Walter Roberson
2023-10-11
Yes, but -2.614279788610316e-08 is less than 0, so you cannot contourf() the 0 level
You might be interested in using
surf(U, Xi, taumin); view(3)
University
2023-10-11
N=[0:0.1:1];
map = [0.95*(1-N') 0.95*(1-N') N'];
fig = openfig('cont1.fig');
fig.Visible = true;
ax = fig.Children(2);
C = ax.Children;
X = C.XData;
Y = C.YData;
Z = C.ZData;
figure();
surf(X, Y, Z); view(3)
colormap(map); colorbar;
That gives me a much better understanding of the data than the contour plot does. The contour plot gives no feeling for the sharp trenches.
University
2023-10-11
更多回答（1 个）
Torsten
2023-10-9
0 个投票
You want to plot imag(taumin(U,xi)) = 0.
Thus use fimplicit:
3 个评论
University
2023-10-9
But in principle, you can compute "taumin" given U and xi ? This would define a function.
Maybe this method is easier to implement:
University
2023-10-10
类别
在 帮助中心 和 File Exchange 中查找有关 Contour Plots 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
