# plot differential equation need help

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Hi. I want to plot (q,y) for three values of x=1,2,3 with two boundary conditions for this differential equation?

how can I write a code

##### 3 Comments

Bjorn Gustavsson
on 24 Jun 2019

Solve it analytically - ought to be simple enough to do by hand. That will give you y(x,q), plot for desired values of q a desired points x.

HTH

### Accepted Answer

Pullak Barik
on 24 Jun 2019

I tried a way out, tell me if it helps-

clc

syms y(x);

syms q;

Dy = diff(y);

ode = diff(y,x,2) + q*y == 10*q; %The equation to solve

cond1 = y(0) == 0; %Initial condition 1

cond2 = Dy(2) == 0; %Initial condition 2

conds = [cond1 cond2];

ySol(x) = dsolve(ode, conds); %Solution in terms of x and q

ySol = simplify(ySol)

syms f1 f2 f3;

f1(q) = ySol(1) %substituting x = 1

f2(q) = ySol(2) %substituting x = 2

f3(q) = ySol(3) %substituting x = 3

%f1, f2, f3 now contain the required functions, plotting them below for brevity

figure;

hold on;

subplot(3,1,1)

title('x=1')

fplot(f1);

subplot(3,1,2)

fplot(f2);

subplot(3,1,3)

fplot(f3);

hold off;

You may refer to the following links for help in understanding the above code-

1) Usage of syms- syms

2) Solving differential equations in MATLAB- Solve Differential Equation

3) Plotting symbolic equations- fplot

##### 4 Comments

Bjorn Gustavsson
on 24 Jun 2019

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