How to set upper x-axis ticks values and locations?

I am trying to set the upper x-axis (ax2) tick values and locations:

x_a = linspace(71.8131,36.9931,10);
y = linspace(0.16,1,10);
x_b = linspace(0.0163,0.0069,10)./0.1016;
figure;
ax1 = axes;
plot(ax1, x_a, y, 'k');
ax2 = axes('Position', ax1.Position, ...
           'XAxisLocation', 'top', ...
           'YAxisLocation', 'right', ...
           'Color', 'none', ...
           'XColor', '#88419d', ...
           'YColor', 'none', ...
           'Box', 'off');
ax2.YLim = ax1.YLim;

new_tick_locations = linspace(30, 80, 6);
new_tick_labels = arrayfun(@(val) sprintf('%.2f', val/500), new_tick_locations, 'UniformOutput', false);

set(ax2, 'XTick', new_tick_locations, 'XTickLabel', new_tick_labels);
% linkaxes([ax1 ax2], 'xy');

hold(ax2, 'on');
plot(ax2, x_b, y, 'r');

This code doesn't show the ax2 ticks at all. I need them to show and to be aligned with the lower x axis labels [30, 40, 50, 60, 70, 80]. How can I fix this? Thank you in advance.

Answer 1

[Aquatris]

You were changing the label name at 30 60, instead of their actual values, so here is one dirty way but I recommend you follow the tilegraph method exaplined here for cleaner and better plot:

x_a = linspace(71.8131,36.9931,10);
y = linspace(0.16,1,10);
x_b = linspace(0.0163,0.0069,10)./0.1016;
figure;
ax1 = axes;
plot(ax1, x_a, y, 'k');
ax2 = axes('Position', ax1.Position, ...
           'XAxisLocation', 'top', ...
           'YAxisLocation', 'right', ...
           'Color', 'none', ...
           'XColor', '#88419d', ...
           'YColor', 'none', ...
           'Box', 'off');
ax2.YLim = ax1.YLim;
new_tick_locations = linspace(30, 80, 6);
new_tick_labels = arrayfun(@(val) sprintf('%.2f', val/500), new_tick_locations, 'UniformOutput', false);
set(ax2, 'XTick', new_tick_locations/500, 'XTickLabel', new_tick_labels);
% linkaxes([ax1 ax2], 'xy');
hold(ax2, 'on');
plot(ax2, x_b, y, 'r');
ax1.Box = 'off';
ax2.XLim = new_tick_locations([1 end])/500;

[Andrea Improta]

Hi, thanks for your answer. I checked the tilegraph method and it is useful, but I would also need the ax2 tick labels to be aligned with the lower x-axis tick labels [30, 40, 50, 60, 70, 80]. So I would like to have [30, 40, 50, 60, 70, 80] on the lower x-axis label and [0.06, 0.08, 0.10, 0.12, 0.14, 0.16] on the upper x-axis label and they should be aligned.

[Aquatris]

Then you can set the xlims to define their minimum and maximum positions:

x_a = linspace(71.8131,36.9931,10);
y = linspace(0.16,1,10);
x_b = linspace(0.0163,0.0069,10)./0.1016;
figure;
ax1 = axes;
plot(ax1, x_a, y, 'k');
ax2 = axes('Position', ax1.Position, ...
           'XAxisLocation', 'top', ...
           'YAxisLocation', 'right', ...
           'Color', 'none', ...
           'XColor', '#88419d', ...
           'YColor', 'none', ...
           'Box', 'off');
ax2.YLim = ax1.YLim;
new_tick_locations = linspace(30, 80, 6);
new_tick_labels = arrayfun(@(val) sprintf('%.2f', val/500), new_tick_locations, 'UniformOutput', false);
set(ax2, 'XTick', new_tick_locations/500, 'XTickLabel', new_tick_labels);
% linkaxes([ax1 ax2], 'xy');
hold(ax2, 'on');
plot(ax2, x_b, y, 'r');
ax1.Box = 'off';
%% to make sure 30 aligns with 0.06 and 80 aligns with 0.16
ax1.XLim = [30 80];
ax2.XLim = [0.06 0.16];

[Andrea Improta]

Thank you!

Answer 2

[Pavan Sahith]

Hello Andrea,

I see that you are facing an issue with the new_tick_locations you are setting for ax2. The new_tick_locations should be within the range of ax2.XLim, which is inherited from ax1.XLim when ax2 is created.

I can see that new_tick_locations you provided (30 to 80) do not match the range of x_b values.To fix this, you need to set the XTick values for ax2 within the range of x_b. you can refer to this sample code:

x_a = linspace(71.8131, 36.9931, 10);
y = linspace(0.16, 1, 10);
x_b = linspace(0.0163, 0.0069, 10) ./ 0.1016;

figure;
ax1 = axes;
plot(ax1, x_a, y, 'k');

ax2 = axes('Position', ax1.Position, ...
           'XAxisLocation', 'top', ...
           'YAxisLocation', 'right', ...
           'Color', 'none', ...
           'XColor', '#88419d', ...
           'YColor', 'none', ...
           'Box', 'off');

ax2.YLim = ax1.YLim;
ax2.XLim = [min(x_b), max(x_b)]; % Set XLim for ax2 to match the range of x_b

% Set new tick locations and labels within the range of x_b
new_tick_locations = linspace(min(x_b), max(x_b), 6);
new_tick_labels = arrayfun(@(val) sprintf('%.2f', val), new_tick_locations, 'UniformOutput', false);

set(ax2, 'XTick', new_tick_locations, 'XTickLabel', new_tick_labels);

hold(ax2, 'on');
plot(ax2, x_b, y, 'r');

following similar adjustments, the ticks for ax2 can be displayed correctly.

you can go through this MathWorks documentation which will help you understand better

• https://www.mathworks.com/help/matlab/creating_plots/graph-with-multiple-x-axes-and-y-axes.html

you can aslo refer to this similar MATLAB answer which might help

• https://www.mathworks.com/matlabcentral/answers/597745

Hope this helps you moving forward

[Andrea Improta]

Hi, thanks for your answer. I was thinking that your solution replaces the ticks that used to be at the locations

new_tick_locations = linspace(min(x_b), max(x_b), 6);

with some new tick values (new_tick_labels). Am I wrong?