plotting functions with two y axes

Hello,

I have to plot two curves on the same graph, same x-axis and different y-axes (right and left). I can't draw the curves with different hatching, different thickness and same black color. I would also like to insert the title of the axes and the legend. Below is the attempt script (R2021b).

Many thanks for the help

figure(1)
x1 = 0:0.1:10;
y1=10+x1.*4;
x2 = 0:0.1:10;
y2=15*sin(x2/2)
t = tiledlayout(1,1);
ax1 = axes(t);
plot(ax1,x1,y1,'-k')
ax1.XColor = 'k';
ax1.YColor = 'k';
ax2 = axes(t);
plot(ax2,x2,y2,'--k')
ax1.XAxisLocation = 'bottom';
ax1.YAxisLocation = 'left';
ax2.XAxisLocation = 'top';
ax2.YAxisLocation = 'right';
ax2.Color = 'none';
ax1.Box = 'off';
ax2.Box = 'off';
grid

Answer 1

[Star Strider]

Use the yyaxis function. It should work with tiledlayout axes.

EDIT — (19 Jan 2025 at 16:10)

I am not certain what result you want, however your code otherwise works as posted.

Try this —

figure(1)
x1 = 0:0.1:10;
y1=10+x1.*4;
 x2 = 0:0.1:10;
y2=15*sin(x2/2)

y2 = 1×101

0 0.7497 1.4975 2.2416 2.9800 3.7111 4.4328 5.1435 5.8413 6.5245 7.1914 7.8403 8.4696 9.0778 9.6633 10.2246 10.7603 11.2692 11.7499 12.2012 12.6221 13.0113 13.3681 13.6915 13.9806 14.2348 14.4534 14.6359 14.7817 14.8907

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t = tiledlayout(1,1);
ax1 = axes(t);
hp(1) = plot(ax1,x1,y1,'-k', DisplayName="(x_1, y_1)");
ax1.XColor = 'k';
ax1.YColor = 'k';
 ax2 = axes(t);
hp(2) =  plot(ax2,x2,y2,'--k', DisplayName="(x_2, y_2)");
 ax1.XAxisLocation = 'bottom';
 ax1.YAxisLocation = 'left';
 ax2.XAxisLocation = 'top';
 ax2.YAxisLocation = 'right';
 ax2.Color = 'none';
ax1.Box = 'off';
ax2.Box = 'off';
grid
xlabel(ax1, 'x_1, x_2')
ylabel(ax1, 'y_1')
ylabel(ax2, 'y_2')
title("Your Title Goes Here")
legend([hp], Location='best')

●

I made some minor changes, however I kept your original code.

.

Answer 2

[Andrea]

dear Star Strider,

thank you very much, it works perfectly

Andrea

[Star Strider]

As always, my pleasure!

Answer 3

[Andrea]

dear all,

I would like to plot multiple curves on the same graph using two y-axes. With your help I managed to plot two curves but I would need to add two more curves on the same axes, for a total of four curves.

I drew the third curve using the traditional “plot” command after the hold on command, if I add the equation of the fourth curve the scale of the y-axis changes compared to that of the current listing. I would like to keep the current scale.

Below is the equation of the curve that I would like to add: x4 = 0:0.1:0.6; y4 = -250.*x1+150. I would also like to add these two curves to the legend. I am adding the current listing.

figure(1) % new figure

x1 = 0:0.1:0.6;

y1 = -500.*x1+300;

x2 = 0:0.1:0.6;

y2 = 29.33.*x2;

x3 = 0:0.1:0.6;

y3 = 14.66.*x2;

x4 = 0:0.1:0.6;

y4 = -250.*x1+150;

t = tiledlayout(1,1);

ax1 = axes(t);

ax2 = axes(t);

hp(1) = plot(ax1,x1,y1,'--k', 'linewidth',1,DisplayName="(x_1, y_1)");

ax1.XColor = 'k';

ax1.YColor = 'k';

%ax3 = axes(t);

hp(2) = plot(ax2,x2,y2,'--k', 'linewidth',2,DisplayName="(x_2, y_2)");

% hp(3) = plot(ax2,x3,y3,'-k', 'linewidth',1,DisplayName="(x_3, y_3)");

% hp(4) = plot(ax2,x4,y4,'-k', 'linewidth',1,DisplayName="(x_4, y_4)");

ax1.XAxisLocation = 'bottom';

ax1.YAxisLocation = 'left';

%ax2.XAxisLocation = 'top';

ax2.YAxisLocation = 'right';

ax2.Color = 'none';

% ax3.YAxisLocation = 'none';

% ax3.Color = 'none';

ax1.Box = 'off';

ax2.Box = 'off';

% ax3.Box = 'off';

grid

xlabel(ax1, 'x1')

ylabel(ax1, 'y1')

ylabel(ax2, 'y2')

%title("Your Title Goes Here")

legend([hp], Location='best')

%legend([hp])

hold on

plot(x3,y3,'-k', 'linewidth',2)

%plot(x4,y4,'-k', 'linewidth',2)

Thanks for your help!

Andrea

[Star Strider]

It’s difficultt for me to figure out what you¹re doing. That aside, I cannot get the added curve (X4,y4) to work with it.

I went a compleetely different route and used the yyaxis function here —

figure(1) % new figure
x1 = 0:0.1:0.6;
y1 = -500.*x1+300;
x2 = 0:0.1:0.6;
y2 = 29.33.*x2;
x3 = 0:0.1:0.6;
y3 = 14.66.*x2;
x4 = 0:0.1:0.6;
y4 = -250.*x1+150;
% t = tiledlayout(1,1);
% ax1 = axes(t);
% ax2 = axes(t);
% hp(1) = plot(ax1,x1,y1,'--k', 'linewidth',1,DisplayName="(x_1, y_1)");
% % hp(3) = plot(ax1, x4, y4, '-.k', DisplayName='(X_4, y_4)');
% ax1.XColor = 'k';
% ax1.YColor = 'k';
% %ax3 = axes(t);
% hp(2) = plot(ax2,x2,y2,'--k', 'linewidth',2,DisplayName="(x_2, y_2)");
% % hp(3) = plot(ax2,x3,y3,'-k', 'linewidth',1,DisplayName="(x_3, y_3)");
% % hp(4) = plot(ax2,x4,y4,'-k', 'linewidth',1,DisplayName="(x_4, y_4)");
% hp(3) = plot(ax1, x4, y4, '-.k', DisplayName='(X_4, y_4)');
% ax1.XAxisLocation = 'bottom';
% ax1.YAxisLocation = 'left';
% %ax2.XAxisLocation = 'top';
% ax2.YAxisLocation = 'right';
% ax2.Color = 'none';
% % ax3.YAxisLocation = 'none';
% % ax3.Color = 'none';
% ax1.Box = 'off';
% ax2.Box = 'off';
% % ax3.Box = 'off';
% grid
% xlabel(ax1, 'x1')
% ylabel(ax1, 'y1')
% ylabel(ax2, 'y2')
% hp
% %title("Your Title Goes Here")
% % legend([hp], Location='best')
% % legend([hp])
% hold on
% plot(x3,y3,'-k', 'linewidth',2)
% %plot(x4,y4,'-k', 'linewidth',2)


figure
yyaxis left
hp(1) = plot(x1,y1,'--k', 'linewidth',1,DisplayName="(x_1, y_1)");
hold on
hp(2) = plot(x2,y2,'--k', 'linewidth',2,DisplayName="(x_2, y_2)");
hold off

yyaxis right
hp(3) = plot(x3,y3,'-k', 'linewidth',1,DisplayName="(x_3, y_3)");
hold on
hp(4) = plot(x4,y4,'-k', 'linewidth',1,DisplayName="(x_4, y_4)");
hold off
grid
legend([hp], Location='best')

●

Make appropriate changes to get your desired result.

.

Answer 4

[Andrea]

Dear Star Strider,

thank you very much for your help, by slightly modifying your script I got the graph I needed. I just can't write the names of the x, y1 and y2 axes. Here the script. Thank you!

Andrea

figure(2)

x1 = 0:0.1:0.6;

y1 = -500.*x1+300;

x2 = 0:0.1:0.6;

y2 = 29.8.*x2;

x3 = 0:0.1:0.6;

y3 = 14.9.*x2;

x4 = 0:0.1:0.6;

y4 = -250.*x1+150;

yyaxis left

hp(4) = plot(x4,y4,'-k', 'linewidth',1,DisplayName="F_1");

hold on

hp(1) = plot(x1,y1,'-k', 'linewidth',2,DisplayName="F_2");

hold on

%hold off

yyaxis right

hp(2) = plot(x2,y2,'--k', 'linewidth',2,DisplayName="P_1");

hp(3) = plot(x3,y3,'--k', 'linewidth',1,DisplayName="P_2");

%hold on

hold off

grid

legend([hp], Location='best')

[Star Strider]

As always, my pleasure!

You can refer to the ylabel calls by using their appropriate axis references, however it is easiest to just put them in the appropriate parts of the code, as I do here.

Try this —

figure(2)
x1 = 0:0.1:0.6;
y1 = -500.*x1+300;
x2 = 0:0.1:0.6;
y2 = 29.8.*x2;
x3 = 0:0.1:0.6;
y3 = 14.9.*x2;
x4 = 0:0.1:0.6;
y4 = -250.*x1+150;
yyaxis left
hp(4) = plot(x4,y4,'-k', 'linewidth',1,DisplayName="F_1");
hold on
hp(1) = plot(x1,y1,'-k', 'linewidth',2,DisplayName="F_2");
hold on
%hold off
ylabel('Left Y-Axis', FontWeight='bold')
yyaxis right
hp(2) = plot(x2,y2,'--k', 'linewidth',2,DisplayName="P_1");
hp(3) = plot(x3,y3,'--k', 'linewidth',1,DisplayName="P_2");
%hold on
hold off
grid
ylabel('Right Y-Axis', FontWeight='bold')
% legend([hp], Location='best')
legend([hp], Location='N')

●

Also, since legend does not appear to be sensitive to the plots on both axes, I put it manually where it wiill not cover any parts of the llines.

.