Matlab AND operation concerning intervals

I am trying to create a simple signal with the following code:

function s = r_tri(t)
if ((t >= 0) & (t <= 3))
  s = (-2/3)*t + 2;
else
  s = 0;
end

Every time I try and plot this I get a blank graph. I assigned t = -1: 0.01: 4; I used the following plot command:

plot (t, r_tri(t))

I also tried this on the command line, and I keep getting 0. Why is this happening? Can you suggest a better way to accomplish this? Thanks.

Answer 1

[Walter Roberson]

function s = r_tri(t)
s = zeros(size(t));
mask = (t >= 0) & (t <= 3);
s(mask) = (-2/3)*t(mask) + 2;

[Aaron Friedman]

Thank you.

Answer 2

[Azzi Abdelmalek]

t = -1: 0.01: 4;
s=zeros(size(t))
idx=t>=0 & t<=3;
s(idx)=(-2/3)*t(idx) + 2;
plot(t,s)

[Aaron Friedman]

Thanks!