how to plot a defined function ?

Question

reza hamzeh 2019-10-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486787-how-to-plot-a-defined-function

评论： Christine Tobler 2019-10-28

hi. i coded 2 functions. now i want to plot N(t) versus T. but it gives me errors. plz help me to do that.

clear;
T=0:0.1:14;
plot(T,N(t))
function pa = partialtranspos(T)
    J=1;B=4;d=4;
    s0=[1 0;0 1];
    sx=[0 1;1 0];
    sy=[0 -1i;1i 0];
    sz=[1 0;0 -1];
    H = 2*J*kron(sz,sz)+B*(kron(sz,s0)+kron(s0,sz))+d*(kron(sx,sy)-kron(sy,sx)); 
    ro = expm(-H/T)/trace(expm(-H/T));
    pa = [ro(1,1) ro(2,1) ro(1,3) ro(2,3);ro(1,2) ro(2,2) ro(1,4) ro(2,4);
        ro(3,1) ro(4,1) ro(3,3) ro(4,3);ro(3,2) ro(4,2) ro(3,4) ro(4,4)];
end
function ne = N(T)
    ne=0.5*(sum(abs(eig(partialtranspose(T))))-1);
end

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Adam 2019-10-22

If it gives you errors then post the error messages here to make it easier for people to help.

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Answer 1

reza hamzeh 2019-10-22

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/486787-how-to-plot-a-defined-function#answer_397678

these are the errors. plz help me.

Error using /

Matrix dimensions must agree.

Error in fortest>partialtranspose (line 13)

ro = expm(-H/T)/trace(expm(-H/T));

Error in fortest>N (line 20)

ne=0.5*(sum(abs(eig(partialtranspose(T))))-1);

Error in fortest (line 4)

plot(T,N(T))

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Christine Tobler 2019-10-28

H is a square matrix, while T is a row vector. The operation H / T is not supported, because this is trying to compute X which solves the linear system X*T = H, which is not possible when H is of size 4-by-4 and T is of size 1-by-141.

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