How to change many loops to recursive function?

1 次查看（过去 30 天）

Paranee Sawad 2019-2-24

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446743-how-to-change-many-loops-to-recursive-function

评论： Paranee Sawad 2019-3-5

Hi, i would like to replace for loops to recursive function. I also would like to have my 5 variables m,al,R0,R1,e in array of (min, max, step,name) because may be in the future i might have more variables so i just add more array and change my function f.

function xm = minfricloop
    
    xm = [ Inf  Inf  Inf  Inf  Inf  Inf];   %For minimization
    
    mmin = 3;
    mmax = 12;
    almin = 0.2;
    almax = 1;
    R0min = 0.014;
    R0max = 0.020;
    R1min = 0.025;
    R1max = 0.030;
    emin = 0.5;
    emax = 0.9;
    rpm = 20000;
    ita = 0.1;
    h0 = 2.51849556599183e-05;
    n = 5;
   
    
   for v = 0 :20
       
      m = mmin + (mmax-mmin)*(v/(20));
        for w = 0 :20
             al = almin + (almax-almin)*(w/(20));
             
             for  x = 0 :20
                R0 = R0min + (R0max-R0min)*(x/(20));
                for y = 0 :20
                    R1 = R1min + (R1max-R1min)*(y/(20));
                    for z = 0 :20
                         e = emin + (emax-emin)*(z/(20));
                       
         k   =  (2*pi*e*(R0+R1)/(2*m))*tan(al*pi/180)/h0;
      
        f = (R1-R0)*(rpm*2*pi*(R0+R1)/(2*60))*ita*(2*pi*e*(R0+R1)/(2*m))*((6/(k+2))+(4*log(k+1)/k))/h0;
       
       if f < xm(6) %For minimization
           xm = [m al R0 R1 e f];
       end
                    end    
                end
             end
        end
   end
end

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Walter Roberson 2019-2-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/446743-how-to-change-many-loops-to-recursive-function#answer_362505

编辑：Walter Roberson 2019-2-24

minfricloop.m

Code attached showing how to use ndgrid for this kind of work.

On my system execution time is less than 0.15 seconds.

22 个评论
显示 20更早的评论隐藏 20更早的评论

Walter Roberson 2019-2-27

In my original code, I used the naming convention that all of the multidimensional arrays of variables are named with trailing _ such as al_ . In the revised code that selects "good" positions, the resulting vectors are named with _g such as al_g .

As I go through your code above, I noticed that you did not use any naming convention about which variables are scalars and which are vectors (or arrays.) Because of that, you have accidentally ended up in a situation where you are calculating vectors of values but you are thinking of them as if they are scalars. In particular, when you are working with arrays, you have one error value for each array location, but your while loop is testing as if you are working with a scalar. You need to figure out what you want to do in this case: do you want to continue the loop only until the condition is false in one location (your current code), or do you want to continue the loop until the condition is false everywhere (that is, all entries fall into range) ? If you are not certain it is possible for the condition to be false everywhere, then you might need to run the calculation over all of the locations individually.

Walter Roberson 2019-3-4

在 MATLAB Online 中打开

Just before you calculate error, set

h0 = max(h0, realmin);

This will prevent h0 from going negative, and so will prevent complex values from being calculated. Somehow it is able to satisfy the error conditions.

Paranee Sawad 2019-3-5

Dear Walter Roberson,

Thank you very much (:

and now i try to recheck the value back, for example in attached file G.m this is the original code when i use to compute h0 if i know the value for m, al, R0, R1 but it seems like when i substitute it didnt return the value h0 same as the value that compute in file minftnormalit123.m

请先登录，再进行评论。