How do I plot an image in Log-Log axis?

Question

Tomas Carvalho 2022-9-15

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1806045-how-do-i-plot-an-image-in-log-log-axis

评论： dpb 2022-9-16

What I want to do is the following: a log-log plot, with areas corresponding to certain categories of flow. Ideally, it would look like the this figure, but with shaded areas.

Currently I am able to determine for each pair of values of x and y, what type of flow it corresponds to. However, I can't plot it over a log-log axis. What I'm gettin looks like this:

The code i'm using is this:

usg=logspace(-1,log10(500),1000); %[m/s]
usl=logspace(-2,log10(50),1000); %[m/s] 
P=findcategory(usl,usg)
figure
h = imagesc(X,Y,P);
h.CDataMapping='direct';
axis xy

where P is a matrix with values from 1 to 8 ( flow categories), where each element is calculated using a pair of elements of usg and usl.

How can I plot this P matrix, in a log-log plot, instead of a linear axis?

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

dpb 2022-9-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1806045-how-do-i-plot-an-image-in-log-log-axis#answer_1054270

在 MATLAB Online 中打开

...
h = imagesc(usl,usg,P);
hAx=gca;
set(hAx,{'XScale','YScale'},{'log','log'})

2 个评论
显示无隐藏无

Tomas Carvalho 2022-9-16

Hey,

Thanks, it worked! I was getting some things mixed up in my head, but then I figured it out. I first thought your solution would create another problem, but I was wrong. It is simple and effective. :)

dpb 2022-9-16

Kewl!

请先登录，再进行评论。

Answer 2

William Rose 2022-9-15

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1806045-how-do-i-plot-an-image-in-log-log-axis#answer_1054285

在 MATLAB Online 中打开

@Tomas Carvalho,

I canot run your code since I do not have findcategory(). I made usg and usl slightly different lengths to be sure that I my surf plot was oriented the right way. Otherwise it is possible to reverse the x and y coordinates in the plot, without knowing it. I set the edgecolor to none in the surface plot, since if you don't, the black edges will dominate the surface.

usg=logspace(-1,log10(500),101); %[m/s]

usl=logspace(-2,log10(50),100); %[m/s]

for i=1:length(usg), for j=1:length(usl)

P(i,j)=floor(log10(usg(i))+log10(usl(j)))+3;

end, end

lusg=log10(usg);

lusl=log10(usl);

figure

surf(lusl,lusg,P,'EdgeColor','none');

view(0,90)

xlabel('log_{10} usl'); ylabel('log_{10} usg');

colorbar

Try that. It is a start. You still have to get the right labels on the color bar...

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Tomas Carvalho 2022-9-16

Hello,

Your solution would also work! However I prefer to keep the logaritmic scale displayed in the traditional way.

Thank you anyway.

请先登录，再进行评论。