Trouble doing loops for specific values

Question

Day Rosli 2016-1-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/265877-trouble-doing-loops-for-specific-values

评论： Star Strider 2016-1-30

Hi. I have problem with loops.

I want to calculate for specific values of P which is 0.5, 0.64, 0.7, 1.0, 6.7. How do I do that?

As from below, this code will let P be 0.5, 0.6, 0.7, 0.8, 0.9. But I dont want it to be like that. I want it as specific values like I mentioned just now.

P=0.5;
  for i=2:5
      P = Pr+0.1;
      sol = bvp4c(@(x,y)VK(x,y,n),@VKbc,sol);
      fprintf('\n');
      fprintf('n \t-Winfinity \n');
      plot(sol.x,-sol.y(3,:),lines{i});
  end

Thank you in advance!

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Answer 1

Star Strider 2016-1-30

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在 MATLAB Online 中打开

Apparently, this is part of a larger script.

I would define ‘P’ in your loop by assigning it as a vector and then referring to individual elements of the vector:

Pv = [0.5, 0.64, 0.7, 1.0, 6.7];
for i=1:length(Pv)
    P = Pv(i);
    sol = bvp4c(@(x,y)VK(x,y,n),@VKbc,sol);
    fprintf('\n');
    fprintf('n \t-Winfinity \n');
    plot(sol.x,-sol.y(3,:),lines{i});
end

I can’t run this so I can’t check it. Make appropriate changes so that it works in your code.

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Day Rosli 2016-1-30

编辑：Day Rosli 2016-1-30

在 MATLAB Online 中打开

Im sorry to trouble you again, but I have tried and im getting confused, should I put Pr or P (at the sol=bvp4c... and everything involving Pr).

function ScriptA
n=0.6;
Pr = [0.5, 0.64, 0.7, 1.0, 6.7];  
infinity=20;
solinit = bvpinit(linspace(0,infinity,30),[0 0 0 -1 0 -1 0]);
sol = bvp4c(@(x,y)VK(x,y,n,Pr),@VKbc,solinit);
x = [0:2:20];
y = deval(sol,x);
figure
plot(sol.x,-sol.y(3,:));    
drawnow
hold on
for i=1:length(Pv)
  Pr = Pv(i);
  sol = bvp4c(@(x,y)VK(x,y,n,Pr),@VKbc,sol);
   lines = {'b-','c-','r-','g-','k-'};
   plot(sol.x,-sol.y(3,:),lines{i});          
end
legend('Pr = 0.5','Pr = 0.64','Pr = 0.7','Pr = 1.0','Pr = 6.7',1);
hold off
function yprime = VK(x,y,n,Pr)
a = ((1-n)/(n+1))*x;
c = (y(4)^2+y(5)^2)^((1-n)/(n+1));
yprime = [ c*y(4)
           c*y(5)
           -2*y(1) - a*c*y(4)
           y(1)^2 - (y(2)+1)^2 + (y(3)+a*y(1))*c*y(4)
           2*y(1)*(y(2)+1) + (y(3)+a*y(1))*c*y(5)
           c*y(7)
           Pr*((y(3)+a*y(1))*c*y(7))
         ];
end
function res = VKbc(ya,yb)
res = [ya(1)
       ya(2)
       ya(3)
       ya(6)+1
       yb(1)
       yb(2)+1
       yb(6)
      ];
end
end