How do I make a secondary Y axis

I need to plot three graph against the same X axis, and to divide right Y axis into two parts as shown in the picture below.

This is how my code looks now, but the third axis is not displayed when the code is run:

figure
yyaxis left
x = [0.00;0.13;0.23;0.35;0.49;0.60;0.72;0.85;0.96;1.08;1.20];
y = [10.35;10.40;10.43;10.50;10.68;10.80;10.99;11.26;11.52;11.89;12.17];
plot(x,y, '-s')
ylabel('Head Ht (m)');

yyaxis right
y2 = [54.4;61.8;70.5;68.4;66.4;72.7;80.0;86.8;95.4;90.1;106.8];
plot(x,y2, '-o')
ylabel ('Power input Pm (W)')
hold on

y3= [0.0;21.9;32.8;51.9;77.4;86.9;96.3;107.8;113.1;138.8;133.2];
plot(x,y3,'-^g')
ylabel ('Pump efficiency (%)')
hold off

grid
xlabel('Volume flow rate Q (dm^3/s)')
legend('Head', 'Power','Efficiency', 'Location', 'NE')

[Sam Chak]

Hi @Kamila Saulenbekova

I added some comments in your code so that you understand what happened.

yyaxis left
...             % business done on the left axis

yyaxis right    % move to the right axis
y2 = [54.4;61.8;70.5;68.4;66.4;72.7;80.0;86.8;95.4;90.1;106.8];
plot(x,y2, '-o')                % done plotting y2
ylabel ('Power input Pm (W)')   % done labeling y2 on the right axis
hold on

y3= [0.0;21.9;32.8;51.9;77.4;86.9;96.3;107.8;113.1;138.8;133.2];
plot(x,y3,'-^g')                % done plotting y3
ylabel ('Pump efficiency (%)')  % labeling y3 overwrites y2 label
hold off

[Kami S]

So how do place y2 and y3 on the right Y axis?

Thank you for your answer, it helped to understand what happened

Answer 1

[Sam Chak]

Hi @Kami S

Perhap a possible solution for manipulating the graph labeling is by using the yticks() command, which allows you to customize the labeling of the y-axis. If the intersections between the graphs are not significant or meaningful for your purpose, you might consider using the following plot instead. It could be a more suitable representation for your needs.

x = [0.00;0.13;0.23;0.35;0.49;0.60;0.72;0.85;0.96;1.08;1.20];

subplot(3,1,1)
y = [10.35;10.40;10.43;10.50;10.68;10.80;10.99;11.26;11.52;11.89;12.17];
plot(x, y, '-s', 'linewidth', 1.5, 'color', '#8D5524'), grid
ylabel('Head Ht (m)');

subplot(3,1,2)
y2 = [54.4;61.8;70.5;68.4;66.4;72.7;80.0;86.8;95.4;90.1;106.8];
plot(x, y2, '-o', 'linewidth', 1.5, 'color', '#C68642'), grid
ylabel ('Pwr input Pm (W)')

subplot(3,1,3)
y3= [0.0;21.9;32.8;51.9;77.4;86.9;96.3;107.8;113.1;138.8;133.2];
plot(x, y3, '-^', 'linewidth', 1.5, 'color', '#F1C27D'), grid
ylabel ('Pump eff (%)')

xlabel('Volume flow rate Q (dm^3/s)')

[Kami S]

It would also work, thank you!

[Sam Chak]

Hi @Kami S,

I'm glad to hear that you like the proposed graphing solution. The approach suggested by @Matt J has successfully addressed the technical aspects of your original question.

Answer 2

[Matt J]

It is, unfortunately, a very awkward thing to do. The datatip will show y3 with an increment of 200, but there may be ways to customize that.

yyaxis left
x = [0.00;0.13;0.23;0.35;0.49;0.60;0.72;0.85;0.96;1.08;1.20];
y = [10.35;10.40;10.43;10.50;10.68;10.80;10.99;11.26;11.52;11.89;12.17];
plot(x,y, '-s')
ylabel('Head Ht (m)');

yyaxis right
y2 = [54.4;61.8;70.5;68.4;66.4;72.7;80.0;86.8;95.4;90.1;106.8];
plot(x,y2, '-o')
ylabel ('Power input Pm (W)          Pump efficiency (%)      ') %<---- combine ylabels

hold on
y3= [0.0;21.9;32.8;51.9;77.4;86.9;96.3;107.8;113.1;138.8;133.2];
plot(x,y3+200,'-^g') %<---- y3 + 200
hold off

yticks([0:25:150,200:25:300])              %
yticklabels([string([0:25:150,0:10:40])])  %<---- manipulate yticks, yticklabels
ylim([0,350])                              %  

grid
xlabel('Volume flow rate Q (dm^3/s)')
legend('Head', 'Power','Efficiency', 'Location', 'NW')