在Matlab指南针图中包括图例

Question

I am using the compass command in matlab to plot wind speeds and direction. I would like to alter the default version to (1) remove the labels within the compass, and (2) draw a legend outside the compass plot to demonstrate the magnitude of each arrow.

Specifically, using the compass is it possible to include a legend which describes the magnitude of the arrows instead of having the values defined on the figure? For example:

rng(0,'twister') % initialize random number generator
M = randn(20,20);
Z = eig(M);

figure
compass(Z)

This is a normal compass plot where the magnitude of each entry is shown by labels on the figure, here they are 1:5. I can remove the labels with:

h = findall(gca,'type','text'); % Find all handles to text labels
legit = {'0','30','60','90','120','150','180','210','240','270','300','330','360',''}; % Define what to keep
idx = ~ismember(get(h,'string'),legit); % Take the others and set them to empty string
set(h(idx),'string',''); 

However, I would now like to include a legend which demonstrates the length of an arrow with a size of say 2 would be. Any ideas on how to do this?

Answer 1

Try some version of this -- after creating the data:

u=abs(Z)
figure(1)
compass(Z)
set(findobj(gcf,'type','text','-and','fontsize',10),'string','')
legend({['z_1 = ',num2str(u(1)),' units'],...
        ['z_2 = ',num2str(u(2)),' units']},...
     'location','southoutside')

I used compass() a lot, but actually i'm not so sure that the font size of the labels are 10, in my (many) compass plots i have used this as a parameter and it worked fine. If it don't, just use the parameter text that findobj() will get all of the text in the figure as well.