ploting 2d graph of a vector

Hey Friends,

I am trying to plot a vecotr (a solution of deritinal eqution) somting like those:

x(t)=Aexp(-3t)

y(t)=Bexp(2t)

Where A B are contecst ( so i am trying to see serveral function)

thanks a lot, Adam.

Answer 1

[Chad Greene]

You've pretty much got it, but you'll need to define a range of t values, and a value for the constants A, and B. You also need to use the * symbol for multiplication.

t = 0:0.1:10; % a range of t values from 0 to 100, steps of 0.1
A = 1; 
B = 2; 
x=A*exp(-3*t);
y=B*exp(2*t);
plot(t,x) 
hold on
plot(t,y)
legend('x(t)','y(t)')

You may also want to set the vertical scale to log scale:

set(gca,'yscale','log')

Answer 2

[adam hafzadi]

oh thank you , but when i am trying to do somtig more seresis its dosn`t work

t = -100:0.1:100; % a range of t values from 0 to 100, steps of 0.1
A = 1; 
B = 2; 
x=A*exp(-2*t)+B*t*exp(-2*t);
y=A*exp(2*t)+B*t*exp(-2*t)+B*exp(-2*t);
plot(t,x) 
hold on
plot(t,y)
legend('x(t)','y(t)')

[Chad Greene]

Oh, yes, that's a quirk of Matlab when you multiply or divide vectors. By default Matlab tries to do a "cross multiplication". To do "dot multiplication" instead, just put a period (.) in front of every multiplication symbol, like this:

t = -100:0.1:100; % a range of t values from -100 to 100, steps of 0.1
A = 1; 
B = 2; 
x=A.*exp(-2.*t)+B.*t.*exp(-2.*t);
y=A.*exp(2.*t)+B.*t.*exp(-2.*t)+B.*exp(-2.*t);
plot(t,x) 
hold on
plot(t,y)
legend('x(t)','y(t)')

[adam hafzadi]

thanks a lot!