plot lines with different x axes on the same MATLAB plot

I am trying to plot two lines with diffenent x axes on the same plot, but matlab kept "avoiding" the first plot and only plot the second one.

(P.S. I checked the y1 and y2, none of them are off the scale of y axis.)

t = tiledlayout(1,1);
ax1 = axes(t);
ax2 = axes(t);

ax2 = 
  Axes with properties:

             XLim: [0 1]
             YLim: [0 1]
           XScale: 'linear'
           YScale: 'linear'
    GridLineStyle: '-'
         Position: [0.1300 0.1100 0.7750 0.8150]
            Units: 'normalized'

  Show all properties

ax1.XAxisLocation = 'bottom';
ax2.XAxisLocation = 'top';
hold(ax1,'on');hold(ax2,'on')
x1 = (1:10);
y1 = sin(x1);
plot(ax1,x1,y1,'r')
hold on
x2 = [11:30];
y2 = cos(x2);
plot(ax2,x2,y2,'b')

Display Data with Multiple Scales and Axes Limits - MATLAB & Simulink (mathworks.com)

The link above are the reference I based on develping this code

Answer 1

[Chris]

Set the axes color of the second plot to 'none' so the lower axis can show through.

t = tiledlayout(1,1);
ax1 = axes(t);
ax2 = axes(t);
ax1.XAxisLocation = 'bottom';
ax2.XAxisLocation = 'top';
x1 = (1:10);
y1 = sin(x1);
plot(ax1,x1,y1,'r')
hold on
x2 = [11:30];
y2 = cos(x2);
%% Important line here
ax2.Color = 'none';
plot(ax2,x2,y2,'b')

[Fan Yang]

@Chris Thanks for the answer, Chris! But I didn't quite get how it worked. Would you mind explaining me why set the color of the second axes realed the first line plot?

[Chris]

@Fan Yang No problem. When an axis is generated, the background is white.

figure('Color',[.7 .7 .7])
plot(1:10,1:10)

When you set the color to 'none', the background becomes transparent.

figure('Color',[.7 .7 .7])
plot(1:10,1:10)
set(gca,'Color','none')

Your first plot was there the whole time, but the second axis was covering it up. If you execute only the steps up to the first plot, you'll see it never shows at all, until you make the other axis transparent.

Does my explanation make sense?

[Fan Yang]

@Chris It does! Thanks for the explanation!