Plotting 2 x-axes against 1 y-axis

Hi,

I am looking to add a second x-axis (measuring time) at the top of the plot seen below. The time corresponds to the number of cycles (approx 275 cycles per day) and should be reaching a maximum value of 20 years (tick mark every 1 or 2 year(s)). I would like to set up the second axis (measuring time) as an array such as: " x2 = 0:1:20; ".I have tried using some of the answers provided to other questions however it is not working for me.

My code for the plot is as follows:

figure(3)

plot(dN, ava)

title('Monte Carlo Simulation 200000','FontSize',14)

xlabel('Number of Cycles')

ylabel('Crack size (mm)')

ylim([0 20])

xlim([0 (total_cycles+50000)])

Thanks!

Answer 1

[Dave B]

You can do something like this by creating a second axes, and in these cases it can be handy to use a tiledlayout to keep the two axes objects aligned. Make sure that you either do you plotting before creating the second axes (if the units of dN match the bottom axis units), or specify ax1/ax2 as the first argument for plot...

ax1=nexttile;
total_cycles = 2e6;
plot(linspace(0, total_cycles, 100), randn(1,100)+10)
xlim([0 total_cycles + 50000])
xlabel('Number of Cycles')
ylabel('Crack size (mm)')

ax2=axes(ax1.Parent, ...
    'XAxisLocation','top','Color','none','XLim',[0 20],'XTick',0:2:20);
linkaxes([ax1 ax2],'y') % This is desirable if you want to plot into either axes

ylim([0 20])
title('Monte Carlo Simulation 200000','FontSize',14)

[Molly Monroy]

Thank you! I tried to use this solution and it has worked other than the ticks from the bottom x-axis are appearing mixed in with the top x-axis (see below). I also need the title of the top x-axis to display 'Time (years)'

[Molly Monroy]

I am also including a horizontal line to indicate a critical crack size using the code below however the line is no longer appearing having updated the code to display a second x-axis.

lineyy = [5 5];
linexx = [0 2e6];
plot(linexx,lineyy,'k-','Color','r','LineWidth',0.5)
hold on

[Dave B]

Ah yes, good point, We can turn off the box to hide the extra tick marks at the top. This will also remove the axis at the right, hopefully that is okay! And we should probably also hide the duplicated y axis, even though you can't really see it.

With respect to your line, you'll want to make sure that you know which of the two axes you're targeting now that there are two. In truth it doesn't matter much because [0 2e6] would work for both, but I think the 'hold on' is out of order.

(You might also consider using yline to draw the line)

ax1=nexttile;
total_cycles = 2e6;
plot(linspace(0, total_cycles, 100), randn(1,100)+10)
xlim([0 total_cycles + 50000])
xlabel('Number of Cycles')
ylabel('Crack size (mm)')
box off

ax2=axes(ax1.Parent, ...
    'XAxisLocation','top','Color','none','XLim',[0 20],'XTick',0:2:20);
linkaxes([ax1 ax2],'y') % This is desirable if you want to plot into either axes
ylim([0 20])
title('Monte Carlo Simulation 200000','FontSize',14)
ax2.YColor='none';
xlabel('Time (years)')

hold(ax1,'on')
lineyy = [5 5];
linexx = [0 2e6];
plot(ax1,linexx,lineyy,'k-','Color','r','LineWidth',0.5)

% note you could also do use yline for simplicity:
% yline(ax1, 5, 'r')

[Molly Monroy]

Ok brilliant thank you, that's working perfectly now!

Answer 2

[Aquatris]

I think this is what you are looking for, see the example for Display Data with Multiple x-Axes and y-Axes

[Molly Monroy]

I've tried using that but my plot was not displaying anything. Thanks though!