Error in using MATLAB PDEPE function - incorrect matrix sizing

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Sarah Snader
Sarah Snader 2018-4-14
评论： Torsten 2018-4-16
Hello!
I am having some issues modifying the code on Matlab Example 2 pdex4 function on the PDEPE help page. I believe the problem is incorrectly sized matrices, but I am not sure where I should be using '.*' vs'*'.
function [x,t,u1, u2]=pdex4attempt(dummy)
close all;
m = 0;
x = [0 0.005 0.01 0.05 0.1 0.2 0.5 0.7 0.9 0.95 0.99 0.995 1];
t = [0 0.005 0.01 0.05 0.1 0.5 1];
sol = pdepe(m,@pdex4pde,@pdex4ic,@pdex4bc,x,t);
u1 = sol(:,:,1);
u2 = sol(:,:,2);
% --------------------------------------------------------------
function [c,f,s] = pdex4pde(x,t,u,DuDx)
Pe=1000;
gamma=2;
phi=0.4;
c = [Pe; 1];
f = [DuDx-Pe.*u(1); 0];
F=(gamma.*u(1)-u(2));
s = [-((1-phi)/phi)*F*Pe; F];
end
% --------------------------------------------------------------
function u0 = pdex4ic(x)
u0 = [0; 0];
end
% --------------------------------------------------------------
function [pl,ql,pr,qr] = pdex4bc(xl,ul,xr,ur,t)
Pe=1000;
beta=0;
pl = [ul(1); 0];
ql = [0; 0];
pr = [-beta+Pe.*ur(1); 0];
qr = [1; 0];
end

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回答（1 个）

Bill Greene
Bill Greene 2018-4-14
The line
f = [DuDx-Pe.*u(1); 0];
is creating a variable f with three rows rather than the correct two rows because DuDx, itself, is dimensioned 2x1. Since you didn't post your equations it is impossible to say what is the correct expression. Do you perhaps want DuDx(1) instead of just DuDx?

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