How can I let a variable include all of the data and not just one value?

I attempting to plot 'u' however it only gives me a constant value. z(5) is a variable that changes with time so is it possible to make 'u' include all of this data instead of just selecting a specific time to create a value?

u=((1+(0.03+betaNN)*0.232)*z(5)-betaNN)/0.699;

pendnum=[z(1)*(gK-0.03); ...
         z(2)*K*(((1-kPOMEGA)*fOMEGA)-((1-kOMEGAP)*fP)); ...
         betaPI*(kPIP*(pHAT-z(3))+(1-kPIP)*(0.03-z(3))); ...
         z(4)*(0.06-pHAT-gK); ...
         (0.03-gK)*z(5)+betaY*(yD-z(5)); ...
         y-yD-z(6)*gK];