# Doubt in solving ODE45

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Susmita Panda on 20 Sep 2021
Edited: Star Strider on 20 Sep 2021
I am trying to solve a differential equation for parameter 'dis' for infinite length of beam which is function of time and space in ode45.I am doubtful about how to consider infinite 'L' in the analysis, as my time is dependent upon v (velocity) and L (length).
I tried solving ode45 as usual taking arbitary L=20 but want to plot 'dis' wrt to space.I need help in plotting.My code has been attached herein.
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Susmita Panda on 20 Sep 2021

Star Strider on 20 Sep 2021
Edited: Star Strider on 20 Sep 2021
It seems that ‘dis’ does not appear anywhere.
L=20;
v=20;%v (m/sec)
T=L/v;
tspan_1=[0:0.001:T];%time range
y0_1=[0;0];%initial conditions
[t1,y1]=ode45(@diffeqn11,tspan_1,y0_1);
figure()
plot(t1, y1(:,1), 'r', 'LineWidth',2)
grid
xlabel('t_1')
ylabel('y_1') function f= diffeqn11(t,y)
A=250;B=20;C=10;j=1;L=20;v=20;a=0.5;%a=x/L
f=zeros(2,1);
f(1)=y(2);
f(2)=(A*sin(j*pi*v*t/L)-B*y(2)-C*y(1))*sin(j*pi*a);%Dimensional
end
EDIT — (20 Sep 2021 at 19:24)
If you have ‘y’ as a function of space and time, this is a partial differential equation.
Express appropriately as a function of both space and time, and then solve it with the pdepe function, or the partial Differential Equation Toolbox functions.
.

Susmita Panda on 20 Sep 2021
Y1 is my "dis" parameter which i need to plot wrt to space

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