Plotting Two Sets of Data on 2 X Axes and 1 Y Axis

Okay, as of now, am having a series of issues:

I am trying to plot two sets of data (1 is in terms of acceleration and the other is in terms of velocity) w/ respect to a single y axis that is in terms of altitude.

1) When I add my axes, they overlap each other. I don't really know how to space out the x axes ticks and labels without having them cutoff from view.

2) I only want to show 1 set of y axis values, but it appears that two values are being plotted. How would I remove one of them?

3) For some reason, when I resize the graph, the two seperate axis plots are not in alignment (they are aligned when the graph is initially created). What can I do to keep the graphs aligned?

Here is my plot, for reference.

Here is my code as well, where vel and acc are two arrays of data that correspond to the x axis values, and altitude is an array that corresponds to the y axes values:

figure(2)
vel = v_entry.*exp(-1/(2*zeta).*exp(-bz));
plot(vel, altitude/1000, 'LineWidth', 4, 'Color', [0.2, 0.6470, 0.810]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
ylabel("Altitude (km)"); xlabel('Velocity (m/s)');
yticks(0:5:55); ylim([0 55]); xticks(0:v_entry/6:v_entry); xlim([0 v_entry]);
ax1 = gca;
hold on
ax1_pos = ax1.Position;
ax2 = axes('Position',ax1_pos,...
    'XAxisLocation','bottom',...
    'Color','none')
hold(ax2,'on')
plot(ax2, acc, altitude./1000,'LineWidth', 4, 'Color', [0.6, 0.4470, 0.7410]);
yticks(0:5:55); ylim([0 55]); xticks(0:450/6:450); xlim([0 450]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
title("Altitude vs Hypersonic Re-Entry Velocity");
xlabel("Acceleration Normalized with Gravity (g)");

[VBBV]

vel = v_entry.*exp(-1/(2*zeta).*exp(-bz));
plot(vel, altitude/1000, 'LineWidth', 4, 'Color', [0.2, 0.6470, 0.810]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
xticks(0:v_entry/6:v_entry); xlim([0 v_entry]);
ax1 = gca;
hold on
ax1_pos = ax1.Position;
ax2 = axes('Position',ax1_pos,...
    'XAxisLocation','bottom',...
    'Color','none')
hold(ax2,'on')
plot(ax2, acc, altitude./1000,'LineWidth', 4, 'Color', [0.6, 0.4470, 0.7410]);
yticks(0:5:55); ylim([0 55]); xticks(0:450/6:450); xlim([0 450]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
title("Altitude vs Hypersonic Re-Entry Velocity");
xlabel({'Velocity (m/s)';'Acceleration Normalized with Gravity (g)'});
ylabel("Altitude (km)");

Use yticks only once as they are same for both plots.

Use string inside xlabel to display both

[Peter Sakkos]

Okay, thanks. But how do I solve the overlapping problem? This is what the graph currently looks like when I resize it:

[VBBV]

%i
vel = v_entry.*exp(-1/(2*zeta).*exp(-bz));
plot(vel, altitude/1000, 'LineWidth', 4, 'Color', [0.2, 0.6470, 0.810]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
xticks(0:v_entry/6:v_entry); xlim([0 v_entry]);
%ax1 = gca;
hold on
%ax1_pos = ax1.Position;
%ax2 = %axes('Position',ax1_pos,... %  %'XAxisLocation','bottom',...
%    'Color','none')
%hold(ax2,'on')
plot(acc, altitude./1000,'LineWidth', 4, 'Color', [0.6, 0.4470, 0.7410]);

You can comment these lines and try again. It seems that you're using axes handle of 1st plot in 2nd figure to change its position. It's not necessary

[Peter Sakkos]

I understand that, but that doesn't solve the problem. I want to plot two sets of data with different scales. For one set of data, the max value is 450. For the other, the max value is 15000. If I plot them on the same scale, the first set of data will look insignificant, plus the sets of data are in different units (m/s vs m/s^2). I want a plot that looks like the image above except:

a) there are two rows of axes values for each set of data (one that goes from 0 to 15000 and the another that goes from o to 450) to show the graphs on two separate scales, and

b) I want the graphs to lign up properly. In the graph I have, for some reason the physical starting point for the y-axis is different for both sets of data, even though they both are supposed to start at 0 and read a y-value of zero when you hover over the point.

[Peter Sakkos]

The problem appears to be that the graphs aren't merged properly, so when an axis label or a title gets added, it scales the two graphs seperately rather than together. If I remove the axis labels and the title, the scaling works properly. Is there a way to fix the two graphs together as one so that this doesn't happen?

[VBBV]

%rue
plot(vel,...)
ax = gca
set(ax,'XTick',[1 2 3...450]);
...
hold on
...
plot(acc,...)
ax1 = gca 
set(ax1,'XTick', [1 2 3...15000]);

Try this by set

[Peter Sakkos]

It looks like your dots are triggering an "Invalid use of operator" error

[VBBV]

The dots ... represent your rest of code as before. Not to use as is

[VBBV]

vel = v_entry.*exp(-1/(2*zeta).*exp(-bz));
plot(vel, altitude/1000, 'LineWidth', 4, 'Color', [0.2, 0.6470, 0.810]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
xticks(linspace(0,v_entry,450)); xlim([0 v_entry]);
ax = gca;
set(ax,'XTick',linspace(0,v_entry,450))
hold on
%ax1_pos = ax1.Position;
%ax2 = axes('Position',ax1_pos,...
 %   'XAxisLocation','bottom',...
  %  'Color','none')
%hold(ax2,'on')
plot(acc, altitude./1000,'LineWidth', 4, 'Color', [0.6, 0.4470, 0.7410]);
yticks(0:5:55); ylim([0 55]); xticks(linspace(0,450,450)); xlim([0 450]);
set(gca, "FontName","Comic Sans MS", "FontSize", 16);
ax1 = gca
set(ax1,'XTick',linspace(0,450,450))
title("Altitude vs Hypersonic Re-Entry Velocity");
xlabel({'Velocity (m/s)';'Acceleration Normalized with Gravity (g)'});
ylabel("Altitude (km)");

Answer 1

[Doddy Kastanya]

To avoid overlap of the two x-axis, you might want to use 'top' for 'XAxisLocation' for ax2.

[Peter Sakkos]

I tried that, and I agree, but I'm still having a sizing issue where the graphs aren't properly aligned.