Plot with two different x-axix

Hello,

I have to plot two different values over a certain depth. Those two values have very different ranges, so I would like one of them (k1) to have its x axis at the top, and the other(NESPN1) its x axix on the bottom. I have tried the mathworks page on double x axis, but it won't work. Can you please help me?

if true

 figure
plot(k1,Depth1)
ax1.XColor = 'r';
ax1.YColor = 'r';
ax1_pos = ax1.Position; % position of first axes
ax2 = axes('Position',ax1_pos,...
    'XAxisLocation','top',...
    'YAxisLocation','left',...
    'Color','none');
plot(NESNP1,Depth1,'Parent',ax2,'Color','k')
set(gca,'Ydir','reverse')
  end

[jonas]

You have not defined ax1 anywhere. Try putting

ax1=gca

before ax1.XColor...

[Lodewijk Pleij]

thanks, but it will still only plot the NESNP1.

if true
 figure
plot(k1,Depth1)
ax1=get(gca) 
ax1.XColor = 'r';
ax1.YColor = 'r';
ax1_pos = ax1.Position; % position of first axes
ax2 = axes('Position',ax1_pos,...
  'XAxisLocation','top',...
  'YAxisLocation','left',...
  'Color','none');
plot(NESNP1,Depth1,'Parent',ax2,'Color','k')
set(gca,'Ydir','reverse')
end

[Guillaume]

@Jonas, answers go in the answer box, not as comments to the question. This is better for you as you can get any credit for comments.

Answer 1

[jonas]

Try this.

clear all;close all

figure;
h=plot(k1,Depth1)
ax1=gca
ax1.XColor = 'r';
ax1.YColor = 'r';
ax1_pos = ax1.Position; % position of first axes
ax2 = axes('Position',ax1_pos,...
    'XAxisLocation','top',...
    'YAxisLocation','left',...
    'Color','none');
plot(NESNP1,Depth1,'Parent',ax2,'Color','k')
set(gca,'Ydir','reverse')
set(ax2,'XAxisLocation','top')
set(ax1,'Ytick',[])

Answer 2

[Guillaume]

Other than the issue with the undefined axis that Jonas answered, it seems that you don't know the correct syntax for plot. If I understood correctly, you're plotting against depth. Hence Depth1 should be the first argument to plot not the second. Overall:

figure;
plot(Depth1, k1);
ax1 = gca;
ax2 = axes('Position', ax1.Position, 'XAxisLocation', 'top', 'YAxisLocation', 'left');
plot(Depth1, NESNP1, 'Parent', ax2, 'Color', 'k');
ax2.Color = 'none';

[Lodewijk Pleij]

Yes this is great! Thanks, the only problem left is that matlab puts both labels on the bottom. Do you know how to put one on the top and the other on the bottom?