How to turn a discrete to a continuous using t

I want to turn a discrete value to a continous using a t as time.

(I also not sure what i asking is correct)

Basically, I want my "y" in continous time

for i=0:1000                   %here we are generating the modulated wave
    if m(i+1)==0
        y(i+1)=c2(i+1);
        else
        y(i+1)=c1(i+1);
    end
end
 
y = mm

[Matlaber]

Or I want to add in "t" for this below

[B, A] = butter(1,0.04, 'low'); % Low Pass Filtered (Low Order)
y = filter(B,A,y);

change to some kind of:

y = ca .* sin(2*pi*t);

Thanks.