How do I perform prelocation when creating an array using a for loop?

for example

Vcruise=[];

HPreq=[];

speedvalue=160;

for i=1:1:speedvalue

Vcruise=[Vcruise,i];

........

Ptotal_fwd=....

......

HPreq=[HPreq,PTotal_fwd];

end

and some graphical operations

Answer 1

[David Hill]

speedvalue=160;
Vcruise=zeros(1,speedvalue);
HPreq=zeros(1,speedvalue);
for i=1:1:speedvalue 
   Vcruise(i)=i;
   Ptotal_fwd=....
   Preq(i)=PTotal_fwd;
end

[sefa arslan]

Thank you