help defining a square wave

Im trying to define a square wave that starts only after 0.01 milliseconds. The code is below. The amplitude and frequency are both correct from the code below but it starts immediately from time 0 rather than from time 0.01, as if the if statement below is always true. what is going wrong?

   t= linspace(0,0.03,1000);
    i_block = 0;
 for k = 1:1000
     t(k)
     if t(k) >= 0.01 
          i_block = mod(t/period, 1) > 0.5;
          i_block = -2*I*i_block + I;
     end;
 end;

[Azzi Abdelmalek]

What is I?

[Joe Koning]

ah sorry, I is the required amplitude, in this case I = 20000; period = 1/2000

Answer 1

[Azzi Abdelmalek]

t= linspace(0,0.03,1000);
period=0.03/10
I=10
i_block = 0;
for k = 1:1000
   t(k)
   if t(k) >= 0.01 
        i_block(k) = mod(t(k)/period, 1) > 0.5;
        i_block(k) = -2*I*i_block(k) + I;
   end;
end;
plot(t, i_block,'r')

[Azzi Abdelmalek]

or

t= linspace(0,0.03,1000);
period=0.03/10
I=10
idx=find(t>=0.01) 
i_block(1:idx(1)-1)=0
i_block(idx) = mod(t(idx)/period, 1) > 0.5
i_block(idx) = -2*I*i_block(idx) + I
plot(t, i_block,'r')

[Joe Koning]

ahhh of course, thankyou

Answer 2

[Wharengaro Ruha]

I need to make a square wave

at 1v for 2000s

then -1v for 2000s

then 1v for 4000s

then -1v for 6000s

then 1v for 2000s