How to put any variable name automatically?

In this program,

a = 1 ;
b=2;
c = zeros(20,1);
d= zeros(20,1);
for k = 1:20
   c(k) = (b+k)^2 + (a+k)^3;
   d(k) = (b+k)^2 - (a+k)^3;

   end

   [maxobjective, iteration1] = max((c));

but i want to pre define objective function, means

 [maxobjective, iteration1] = max((c)); or
 [maxobjective, iteration1] = max((d));

put automatically like below.

objfun = c; %or d
a = 1 ;
b=2;
c = zeros(20,1);
d= zeros(20,1);
for k = 1:20
   c(k) = (b+k)^2 + (a+k)^3;
   d(k) = (b+k)^2 - (a+k)^3;

   end

   [maxobjective, iteration1] = max((objfun));

Answer 1

[Walter Roberson]

Use the same variable for both, but make it a cell array. And make objfun the index of the cell to use.

[Triveni]

Ya, done.

objfun = 1; %or 2
a = 1 ;
b=2;
c = zeros(20,1);
d= zeros(20,1);
for k = 1:20
 c(k) = (b+k)^2 + (a+k)^3;
 d(k) = (b+k)^2 - (a+k)^3;

 end
 if objfun == 1
 [maxobjective, iteration1] = max((c));
 end

 if objfun == 2
 [maxobjective, iteration1] = max((d));
 end

[Walter Roberson]

objfun = 1; %or 2
a = 1 ;
b=2;
c_d{1} = zeros(20,1);
c_d{2} = zeros(20,1);
for k = 1:20
  c_d{1}(k) = (b+k)^2 + (a+k)^3;
  c_d{2}(k) = (b+k)^2 - (a+k)^3;
end
[maxobjective, iteration1] = max(c_d{objfun});