Not enough input arguments Error in bvpfcn (line 5) dydx = [y(2)*(U*y​(2)+K*y(1)​)/D];

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Naveen Krish
Naveen Krish 2022-3-15
评论： Walter Roberson 2022-3-18
Error in bvpfcn (line 5) dydx = [y(2)*(U*y(2)+K*y(1))/D];
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Naveen Krish
Naveen Krish 2022-3-15
编辑：Walter Roberson 2022-3-15
function dydx = ode(y,x) % equation to solve
y1 = y(1);
y2= y(2);
dy1_dx = y(2);
dy2_dx = [U*y2+K*y1/D];
dy_dx = [dy_dx; dy2_dx];
end

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回答（1 个）

Jan
Jan 2022-3-15
编辑：Jan 2022-3-16
r = bvp4c(ode,bc,solinit);
% ^^^
This is a call of the function ode() without input arguments. You want to provide a function handle instead:
r = bvp4c(@ode,bc,solinit);
% ^
This will fail also:
function dydx = ode(y,x) % equation to solve
y1 = y(1);
y2= y(2);
dy1_dx = y(2);
dy2_dx = [U*y2+K*y1/D];
dy_dx = [dy_dx; dy2_dx];
end
The function replies "dydx", but you define "dy_dx". Easier:
function dydx = ode(y, x)
D = 0.1; % m2/s
U = 1; % m/s
K = 1e-6; % 1/s
dydx = [y(2); ...
(U * y(2) + K * y(1)) / D]; % EDITED, parentheses added
end
Remember that 1*10^-6 is a multiplication and an expensive power operation, while 1e-6 is a cheap constant.
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Naveen Krish
Naveen Krish 2022-3-18
Unrecognized function or variable 'solinit'.
Error in bvpfcn (line 1)
r = bvp4c(@ode,@bc,solinit);

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