why in the following code the value of gbest is not updating with each iteration and showing Infinity as a outcome..

fgbest=Inf;

for j=1:Popsize

          % Generate Random Solution
          pop(:,j)=randi([500,2000],10,1);

           [obj]=objfn(pop,it);
  % 
  %         % Evaluation
          obj1(j,1) = obj(j,1);%
  % 
          % Update the Personal Best
          pbest(:,j) = pop(:,j);% pbest
          fpbest(j,1) =obj1(j,1);% objective function
  % 
  %         % Update Global Best
          if  fpbest(j,1) < fgbest
              gbest = pbest(:,j);% gbest
          end
 end

[Geoff Hayes]

sharad - what is your objective function, objfn? Have you stepped through the code to see what is happening and, in particular, what this function is returning? Also, for your condition

 if  fpbest(j,1) < fgbest
     gbest = pbest(:,j);% gbest
 end

I think that you want to be using just one of gbest or fgbest. (What is the difference between the two?) Since you are trying to find the global best, you will always want to compare against the last best found solution. So something like

 if  fpbest(j,1) < fgbest
     fgbest = pbest(:,j);
 end

may be what you really want.