Legends display incorrect markers

The Incorrect markers will appear next to the strings in the legend.

for k = 1:size(Scattering,1)
  hold on
  if grade(k) == 0
      figure(1)
      plot(XS(k,x),XS(k,y),'bo')
  elseif grade(k) >= 1
      figure(1)
      plot(XS(k,x),XS(k,y),'ro')
  end
  if grade(k) == 13 || grade(k) == 14
      figure(2)
      plot(XS(k,x),XS(k,y),'rx')
  elseif grade(k) >= 16
      figure(2)
      plot(XS(k,x),XS(k,y),'kx')
  end
end
set(get(get(figure(1),'children'),'xLabel'),'string',sprintf('PC%d',x))
set(get(get(figure(2),'children'),'xLabel'),'string',sprintf('PC%d',x))
set(get(get(figure(1),'children'),'yLabel'),'string',sprintf('PC%d',y))
set(get(get(figure(2),'children'),'yLabel'),'string',sprintf('PC%d',y))
set(get(get(figure(1),'children'),'title'),'string','Benign vs. Malignant')
set(get(get(figure(2),'children'),'title'),'string','High grade vs. Low grade cancer')
%get(get(figure(2),'children'),'children')
%legends correspond to plot order and not to given plots
legend(get(get(figure(1),'children'),'children'),'Benign','Malignant','Location','NorthEastOutside')
legend(get(get(figure(2),'children'),'children'),'High Grade','Low Grade','Location','NorthEastOutside')
hold off

I attempted to create a legend with a blue circle next benign and a red circle next to malignant. Instead there are blue circles next to both, and not coincidentally the last two objects plotted on the axes were both blue circles.

[Matt Fig]

Please provide some sample data that will:

1. Allow your code to actually run.
2. Generate the problem you want investigated.

[Ryan]

In the most recent run, Scattering was a 150x41 matrix, grade was a 150x1 matrix, and XS was a 150x5 matrix. I forgot to mention this warning pops up.

Warning: Ignoring extra legend entries. 
> In legend at 291
In PLSAnalysis_Scattering at 45 
Warning: Ignoring extra legend entries. 
> In legend at 291
In PLSAnalysis_Scattering at 46

[Ryan]

And x=1 y=2...oops

Answer 1

[Matt Fig]

I would dispense with keeping track of all that stuff anyway. Switching current figures in a loop, keeping track of handles, calling great-grandparents and children, setting the string property of xlabel and title objects and all? Not here!

This is much more straightforward and easier to understand:

figure
idx = grade==0;
plot(XS(idx,1),XS(idx,2),'bo')
hold on
idx = grade>=1;
plot(XS(idx,1),XS(idx,2),'ro')
xlabel(sprintf('PC%d',x))
ylabel(sprintf('PC%d',y))
title('Benign vs. Malignant')
legend('Benign','Malignant','Location','NorthEastOutside')
figure
idx = grade==13 | grade==14;
plot(XS(idx,1),XS(idx,2),'rx')
hold on
idx = grade>=16;
plot(XS(idx,1),XS(idx,2),'kx')
xlabel(sprintf('PC%d',x))
ylabel(sprintf('PC%d',y))
title('High grade vs. Low grade cancer')
legend('High Grade','Low Grade','Location','NorthEastOutside')

Answer 2

[Sean de Wolski]

Apparently the children order being returned is not what you expect. I would recommend explicitly saving the handles rather than getting children's grandchildren's great grandparents!

[Ryan]

Had a lot of trouble with this method. I still couldn't get the second legend to display correctly, and I have no idea why I needed two hold on's.

hold on
fig1hand = figure(1);
fig2hand = figure(2);
for k = 1:size(Scattering,1)
  hold on
  if grade(k) == 0
      plotbenhand = plot(get(fig1hand,'children'),XS(k,x),XS(k,y),'bo');
  elseif grade(k) >= 1
      plotmalhand = plot(get(fig1hand,'children'),XS(k,x),XS(k,y),'ro');
  end
  if grade(k) == 13 || grade(k) == 14
      plot(get(fig2hand,'children'),XS(k,x),XS(k,y),'rx')
  elseif grade(k) >= 16
      plot(get(fig2hand,'children'),XS(k,x),XS(k,y),'kx')
  end
end
hold off
legend(get(fig1hand,'children'),['mal';'ben'])
legend(get(fig2hand,'children'),['hig';'low'])

[Sean de Wolski]

You need the second hold on because you create the figures after the call to the first one. Thus they don't see the first one.

However, I don't see why you need either, considering you're only plotting to each figure once...