Unable to perform assignment because the left and right sides have a different number of elements. Can anyone help me with this?

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Md Mezbah Uddin
Md Mezbah Uddin 2018-11-29
评论： madhan ravi 2018-11-29
clear all
clc
%boundary condition
x1=[0 0.0069 0.1565 0.3396 0.4666 0.6004 0.7021 0.8286 0.8868 0.9165 0.9561 0.9840 1.0];
P=[57.52 58.2 126 175.3 189.5 224.3 236 250 259 261.11 264.45 266.53 271];
% length(x1)
% length(P)
p=polyfit(x1,P,4);
dpdx=polyder(p);
y10=9.029e-5;
I0=0;
xspan=[1e-5 0.99999];
[x,y]=ode15s(@gibbs,xspan,[y10 I0])
plot(x,y)
function dy= gibbs(x,y)
x1=[0 0.0069 0.1565 0.3396 0.4666 0.6004 0.7021 0.8286 0.8868 0.9165 0.9561 0.9840 1.0];
P=[57.52 58.2 126 175.3 189.5 224.3 236 250 259 261.11 264.45 266.53 271];
p=polyfit(x1,P,4);
dpdx=polyder(p);
dy=zeros(2,1);
P1v=271;
P2v=57.52
Pr=p(1,1)*x^4+p(1,2)*x^3+p(1,3)*x^2+p(1,4)*x+p(1,5);
dP=(dpdx(1,1)*x^3+dpdx(1,2)*x^2+dpdx(1,3)*x+dpdx(1,4));
% dP=-1447.1*x^3+2724.2*x^2-1780.8*x+556.29;
% Pr=-361.764*x^4+908.0529*x^3-890.3941*x^2+556.2994*x+56.2611;
dy(1)=(y.*(1-y)./(y-x)).*(dP)./(Pr) ;
dy(2)=log((y.*Pr)./(x.*P1v))-log((1-y).*Pr./((1-x).*P2v));
end

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回答（1 个）

Luna
Luna 2018-11-29
Hi,
Change like below:
dy=zeros(2,2);
dy(:,1)=(y.*(1-y)./(y-x)).*(dP)./(Pr) ;
dy(:,2)=log((y.*Pr)./(x.*P1v))-log((1-y).*Pr./((1-x).*P2v));
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Luna
Luna 2018-11-29
Your code in below gives 2x1 vectors.
(y.*(1-y)./(y-x)).*(dP)./(Pr) % result [11.1169 0]'
log((y.*Pr)./(x.*P1v))-log((1-y).*Pr./((1-x).*P2v)) % result [0.6505 -Inf]'
And you are trying to assign them dy(1) and dy(2) which represents just first and second element of a double array.
Which values you are going to use?

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