Input conditional sine wave

Hi, I am trying to input a signal which is a sine wave between 3 and 7 seconds and zero everywhere else. I am trying to create an 'for loop' to do this by indexing the time vector but I can't make it work, the graph just displays nothing (assuming matlab thinks x = 0 for all time?)...is there anything I've missed?

t = [0:0.1:10];

for k=1:length(t)

if t(k)>=3 && t(k)<=7

      x = 5*sin(4*pi *t);

else
    x = 0;
end
end

plot(t,x)

Any help would be greatly appreciated :)

Answer 1

[KSSV]

t = 0:0.1:10;
x = 5*sin(4*pi *t);
x(t<3) = 0 ;
x(t>7) = 0 ;
plot(t,x)