# Subplot for individual for loop angle

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Jun Hong Wang on 17 Nov 2021
Commented: Jun Hong Wang on 24 Nov 2021
I am trying to do subplot for each angle like the one below. But when I try to do it it only show the sine wave for all the angle on subplot(2,2,1).
Below is my code
for angle = [0.2 , deg2rad(7.5), deg2rad(30), deg2rad(45)]
for i=1
subplot(2,2,i)
%theta(0) = 0.2 rad
initial_x = [angle;0];
[t,x] = ode45(@fun, t, initial_x);
%figure
hold on
%graph for 0.2 rad of Part A (Non-Linear), plotted in red
plot(t,x(:,2))
%theta(0) = 0.2 rad
initial_y1 = [angle;0];
[t,y] = ode45(@fun1, t, initial_y1);
%graph for 0.2 rad of Part B (Linear), plotted in blue
plot(t,y(:,2))
grid on
title("Angular Velocity VS Time (" +angle+ " rad)")
xlabel('Time (s)')
ylabel('Angular Velocity (\omega)')
legend('Part A (Non-Linear)','Part B (Linear)')
hold off
end
end
##### 2 CommentsShowHide 1 older comment
Jun Hong Wang on 18 Nov 2021
My bad should have clarify that the above graph is the graph I want to make but with the current code I have I can only get the result below. I have also included who whole code
close all
clear
%Graph for velocity against time
%0.1 rad, 0.13 rad, 0.52 rad, 0.79 rad are plotted together
global g l
g = 9.81; %gravity
l = 9.81; %length
dt = 0.001; %time interval
t = 0:dt:10; %time from 0 to 10
for angle = [0.2 , deg2rad(7.5), deg2rad(30), deg2rad(45)]
for i=1
subplot(2,2,i)
%theta(0) = 0.2 rad
initial_x = [angle;0];
[t,x] = ode45(@fun, t, initial_x);
%figure
hold on
%graph for 0.2 rad of Part A (Non-Linear), plotted in red
plot(t,x(:,2))
%theta(0) = 0.2 rad
initial_y1 = [angle;0];
[t,y] = ode45(@fun1, t, initial_y1);
%graph for 0.2 rad of Part B (Linear), plotted in blue
plot(t,y(:,2))
grid on
title(sprintf('Angular Velocity VS Time (%.2f rad)', angle));
xlabel('Time (s)')
ylabel('Angular Velocity (\omega)')
legend('Part A (Non-Linear)','Part B (Linear)')
hold off
end
end
function dxdt = fun(~,x) %Non-linear function (Part A)
global g l
dx1dt = x(2);
dx2dt = -(g/l)*sin(x(1));
dxdt = [dx1dt;dx2dt];
end
function dydt = fun1(~,y) %Linear function (Part B)
global g l
dy1dt = y(2);
dy2dt = -(g/l)*(y(1));
dydt = [dy1dt;dy2dt];
end

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### Accepted Answer

Alamanda Ponappa Poovaya on 24 Nov 2021
Hi,
the reason the graph isn't being plotted the way you expect is because your nested for loop structure is incorrect for this case. You want 4 plots on different subplots. Refer to the code below. It is identical to your code but I've modified the for loops. Only one for loop is required for plotting, and a variable i is used to select the different subplots
close all
clear
%Graph for velocity against time
%0.1 rad, 0.13 rad, 0.52 rad, 0.79 rad are plotted together
global g l
g = 9.81; %gravity
l = 9.81; %length
dt = 0.001; %time interval
t = 0:dt:10; %time from 0 to 10
%start at subplot 2,2,1
i = 1;
for angle = [0.2 , deg2rad(7.5), deg2rad(30), deg2rad(45)]
subplot(2,2,i);
% increment i, so next plot is on next subplot and so on
i = i+1;
%theta(0) = 0.2 rad
initial_x = [angle;0];
[t,x] = ode45(@fun, t, initial_x);
%figure
hold on
%graph for 0.2 rad of Part A (Non-Linear), plotted in red
plot(t,x(:,2))
%theta(0) = 0.2 rad
initial_y1 = [angle;0];
[t,y] = ode45(@fun1, t, initial_y1);
%graph for 0.2 rad of Part B (Linear), plotted in blue
plot(t,y(:,2))
grid on
title(sprintf('Angular Velocity VS Time (%.2f rad)', angle));
xlabel('Time (s)')
ylabel('Angular Velocity (\omega)')
legend('Part A (Non-Linear)','Part B (Linear)')
hold off
end
function dxdt = fun(~,x) %Non-linear function (Part A)
global g l
dx1dt = x(2);
dx2dt = -(g/l)*sin(x(1));
dxdt = [dx1dt;dx2dt];
end
function dydt = fun1(~,y) %Linear function (Part B)
global g l
dy1dt = y(2);
dy2dt = -(g/l)*(y(1));
dydt = [dy1dt;dy2dt];
end
##### 1 CommentShowHide None
Jun Hong Wang on 24 Nov 2021
Thank you so much! Really appreciate it.

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