what is wrong with my code, i am trying to plot below

for t = 1:.01:10;
   if t <= pi
        x = 1.41.*exp(-t).*sin(t+0.785);
    elseif t > pi
        x = 1.41.*exp(-t).*sin(t+0.785)-(exp(-(t-pi).*sin(t-pi)));
    end
end
 
plot(t,x)   

xlabel('t')
ylabel('X(t)')

Answer 1

[the cyclist]

In every iteration of the for loop, you are simply overwriting x, over and over.

Instead, you need to define a vector for x, too. Here is one way:

t = 1:.01:10;

tCount = numel(t);

x = zeros(tCount,1);

for nt = 1:tCount
   if t(nt) <= pi
        x(nt) = 1.41.*exp(-t(nt)).*sin(t(nt)+0.785);
    elseif t(nt) > pi
        x(nt) = 1.41.*exp(-t(nt)).*sin(t(nt)+0.785)-(exp(-(t(nt)-pi).*sin(t(nt)-pi)));
    end
end
 
plot(t,x)   

xlabel('t')
ylabel('X(t)')

Answer 2

[the cyclist]

FYI, there is a much more efficient solution, which is to avoid the for loop altogether:

t = 1:.01:10;

x = zeros(size(t));

x(t<=pi) = 1.41.*exp(-t(t<=pi)).*sin(t(t<=pi)+0.785);
x(t>pi) = 1.41.*exp(-t(t>pi)).*sin(t(t>pi)+0.785)-(exp(-(t(t>pi)-pi).*sin(t(t>pi)-pi)));

plot(t,x)   

xlabel('t')
ylabel('X(t)')