using fsolve to solve non-linear equations in matlab












0












$begingroup$


I'm trying to solve this system equations in matlab



syms  y z i

x=[29.6,29.4,34.4,35.1,34.3,36.1,31.6,32.9,31.5,28.3,37.1,28.4,27.3,33.1,31.3,33.1]

n = 16

eqns = sym(zeros(1, 2 * n));



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + exp(-((x(j) - y) / z));

    end

    a = i/z - a/z;

    eqns(i) = a == 0;

end



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + ((x(j) - y)/z^2) - ((x(i) - y)/z^2) * exp((-x(j) + y)/z);

    end

    a = -i/z + a;

    eqns(i + 16) = a == 0;

end

eqns

solve(eqns, [y, z])


But it seems solve can't solve this one.



Warning: Cannot find explicit solution. 

> In solve (line 316)

  In xx (line 24)


I tried to use fslove but by follow the tutorial at https://www.mathworks.com/help/optim/ug/fsolve.html?s_tid=gn_loc_drop



but when I tried to enter



function F = root2d(x)



F(1) = exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);

F(2) = x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5;


matlab throw error.



Can someone please help me?



Thank you.



P/S: Can this problem be solved with singular?I'm trying to solve this system equations in matlab






systems-of-equations matlab singular-cas







share|cite|improve this question









$endgroup$












  • $begingroup$
    Your fsolve code doesn't match the system of 32 equations you're trying to solve symbolically. It's not clear what you're trying to do. I'm also not sure why you're using i as a symbolic variable and the re-defining it in your for loops.
    $endgroup$
    – horchler
    Mar 8 '17 at 19:59
















0












$begingroup$


I'm trying to solve this system equations in matlab



syms  y z i

x=[29.6,29.4,34.4,35.1,34.3,36.1,31.6,32.9,31.5,28.3,37.1,28.4,27.3,33.1,31.3,33.1]

n = 16

eqns = sym(zeros(1, 2 * n));



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + exp(-((x(j) - y) / z));

    end

    a = i/z - a/z;

    eqns(i) = a == 0;

end



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + ((x(j) - y)/z^2) - ((x(i) - y)/z^2) * exp((-x(j) + y)/z);

    end

    a = -i/z + a;

    eqns(i + 16) = a == 0;

end

eqns

solve(eqns, [y, z])


But it seems solve can't solve this one.



Warning: Cannot find explicit solution. 

> In solve (line 316)

  In xx (line 24)


I tried to use fslove but by follow the tutorial at https://www.mathworks.com/help/optim/ug/fsolve.html?s_tid=gn_loc_drop



but when I tried to enter



function F = root2d(x)



F(1) = exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);

F(2) = x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5;


matlab throw error.



Can someone please help me?



Thank you.



P/S: Can this problem be solved with singular?I'm trying to solve this system equations in matlab






systems-of-equations matlab singular-cas







share|cite|improve this question









$endgroup$












  • $begingroup$
    Your fsolve code doesn't match the system of 32 equations you're trying to solve symbolically. It's not clear what you're trying to do. I'm also not sure why you're using i as a symbolic variable and the re-defining it in your for loops.
    $endgroup$
    – horchler
    Mar 8 '17 at 19:59














0












0








0





$begingroup$


I'm trying to solve this system equations in matlab



syms  y z i

x=[29.6,29.4,34.4,35.1,34.3,36.1,31.6,32.9,31.5,28.3,37.1,28.4,27.3,33.1,31.3,33.1]

n = 16

eqns = sym(zeros(1, 2 * n));



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + exp(-((x(j) - y) / z));

    end

    a = i/z - a/z;

    eqns(i) = a == 0;

end



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + ((x(j) - y)/z^2) - ((x(i) - y)/z^2) * exp((-x(j) + y)/z);

    end

    a = -i/z + a;

    eqns(i + 16) = a == 0;

end

eqns

solve(eqns, [y, z])


But it seems solve can't solve this one.



Warning: Cannot find explicit solution. 

> In solve (line 316)

  In xx (line 24)


I tried to use fslove but by follow the tutorial at https://www.mathworks.com/help/optim/ug/fsolve.html?s_tid=gn_loc_drop



but when I tried to enter



function F = root2d(x)



F(1) = exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);

F(2) = x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5;


matlab throw error.



Can someone please help me?



Thank you.



P/S: Can this problem be solved with singular?I'm trying to solve this system equations in matlab






systems-of-equations matlab singular-cas







share|cite|improve this question









$endgroup$




I'm trying to solve this system equations in matlab



syms  y z i

x=[29.6,29.4,34.4,35.1,34.3,36.1,31.6,32.9,31.5,28.3,37.1,28.4,27.3,33.1,31.3,33.1]

n = 16

eqns = sym(zeros(1, 2 * n));



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + exp(-((x(j) - y) / z));

    end

    a = i/z - a/z;

    eqns(i) = a == 0;

end



for i = 1:n

    a = 0;

    for j = 1:i

        a = a + ((x(j) - y)/z^2) - ((x(i) - y)/z^2) * exp((-x(j) + y)/z);

    end

    a = -i/z + a;

    eqns(i + 16) = a == 0;

end

eqns

solve(eqns, [y, z])


But it seems solve can't solve this one.



Warning: Cannot find explicit solution. 

> In solve (line 316)

  In xx (line 24)


I tried to use fslove but by follow the tutorial at https://www.mathworks.com/help/optim/ug/fsolve.html?s_tid=gn_loc_drop



but when I tried to enter



function F = root2d(x)



F(1) = exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);

F(2) = x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5;


matlab throw error.



Can someone please help me?



Thank you.



P/S: Can this problem be solved with singular?I'm trying to solve this system equations in matlab






systems-of-equations matlab singular-cas




systems-of-equations matlab singular-cas






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Mar 8 '17 at 3:05









Lan Anh NguyễnLan Anh Nguyễn

11




11












  • $begingroup$
    Your fsolve code doesn't match the system of 32 equations you're trying to solve symbolically. It's not clear what you're trying to do. I'm also not sure why you're using i as a symbolic variable and the re-defining it in your for loops.
    $endgroup$
    – horchler
    Mar 8 '17 at 19:59


















  • $begingroup$
    Your fsolve code doesn't match the system of 32 equations you're trying to solve symbolically. It's not clear what you're trying to do. I'm also not sure why you're using i as a symbolic variable and the re-defining it in your for loops.
    $endgroup$
    – horchler
    Mar 8 '17 at 19:59
















$begingroup$
Your fsolve code doesn't match the system of 32 equations you're trying to solve symbolically. It's not clear what you're trying to do. I'm also not sure why you're using i as a symbolic variable and the re-defining it in your for loops.
$endgroup$
– horchler
Mar 8 '17 at 19:59




$begingroup$
Your fsolve code doesn't match the system of 32 equations you're trying to solve symbolically. It's not clear what you're trying to do. I'm also not sure why you're using i as a symbolic variable and the re-defining it in your for loops.
$endgroup$
– horchler
Mar 8 '17 at 19:59










1 Answer
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$begingroup$

It's not clear what the problem is without being given the error, but:



F=@(x) [exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5];

x0=[1;1];

fsolve(F,x0)


worked for me. You can do this using "function F = ..." syntax, but then you need to write @F in the call to fsolve.






share|cite|improve this answer









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    $begingroup$

    It's not clear what the problem is without being given the error, but:



    F=@(x) [exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5];
    
x0=[1;1];
    
fsolve(F,x0)


    worked for me. You can do this using "function F = ..." syntax, but then you need to write @F in the call to fsolve.






    share|cite|improve this answer









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      0












      $begingroup$

      It's not clear what the problem is without being given the error, but:



      F=@(x) [exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5];
      
x0=[1;1];
      
fsolve(F,x0)


      worked for me. You can do this using "function F = ..." syntax, but then you need to write @F in the call to fsolve.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        It's not clear what the problem is without being given the error, but:



        F=@(x) [exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5];
        
x0=[1;1];
        
fsolve(F,x0)


        worked for me. You can do this using "function F = ..." syntax, but then you need to write @F in the call to fsolve.






        share|cite|improve this answer









        $endgroup$



        It's not clear what the problem is without being given the error, but:



        F=@(x) [exp(-exp(-(x(1)+x(2)))) - x(2)*(1+x(1)^2);x(1)*cos(x(2)) + x(2)*sin(x(1)) - 0.5];
        
x0=[1;1];
        
fsolve(F,x0)


        worked for me. You can do this using "function F = ..." syntax, but then you need to write @F in the call to fsolve.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Mar 8 '17 at 3:36









        IanIan

        68.2k25388




        68.2k25388






























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