# help me to find error in this file?

조회 수: 2(최근 30일)
Nk 2023년 1월 30일
답변: the cyclist 2023년 1월 30일
function Needle1
a=0.2;
solinit= bvpinit(linspace(a,40,100),[0 0 0]);
sol = bvp4c(@Needle1ode,@Needle1bc,solinit);
eta = sol.x;
f = sol.y;
disp(f(3,1))
function dfdeta = Needle1ode(eta,~)
Pr=3.0;thetha=2.0;Nr=10;Ec=0.3;
dfdeta = [ f(2)
f(3)
-(1/(2*eta))*(f(1)*f(3)+2*f(3))
f(5)
-(f(5)/eta*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3)+Pr*f(1)*f(5)/2*eta*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3 +4*Ec*Pr*(f(3))^2/(1+4/3*Nr*(f(4)*(thetha-1)+1)^(3)+2*f(4)*(f(4)*(thetha-1)+1)^(3)/(3*eta*Nr)*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3)+4*f(5)^2*(thetha-1)*(f(4)*(thetha-1)+1)^2/(Nr*(1+4/3*Nr(f(4)*(thetha-1)+1)^3
];
function res = Needle1bc(f0,finf)
a=0.2;e=0.3;
res = [f0(1)-(a*e/2)
f0(2)-e/2
finf(2)-(1-e)/2
f0(1)-1
finf(1)-0
];
error is in this line:
-(f(5)/eta*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3)+Pr*f(1)*f(5)/2*eta*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3 +4*Ec*Pr*(f(3))^2/(1+4/3*Nr*(f(4)*(thetha-1)+1)^(3)+2*f(4)*(f(4)*(thetha-1)+1)^(3)/(3*eta*Nr)*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3)+4*f(5)^2*(thetha-1)*(f(4)*(thetha-1)+1)^2/(Nr*(1+4/3*Nr(f(4)*(thetha-1)+1)^3
];
and the error shown was;
>> Needle1
Error: File: Needle1.m Line: 16 Column: 309
Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for
mismatched delimiters.

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### 채택된 답변

the cyclist 2023년 1월 30일
The error seems to be that you are missing parentheses, or they are otherwise mismatched. We could guess at where they are missing, but could not guarantee that the resulting expression is the one you need.
Rather than trying to find the error for you, I will suggest the following strategy for you to find the error yourself.
As you already can see, an expression like
-(f(5)/eta*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3)+Pr*f(1)*f(5)/2*eta*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3 +4*Ec*Pr*(f(3))^2/(1+4/3*Nr*(f(4)*(thetha-1)+1)^(3)+2*f(4)*(f(4)*(thetha-1)+1)^(3)/(3*eta*Nr)*(1+4/3*Nr*(f(4)*(thetha-1)+1)^3)+4*f(5)^2*(thetha-1)*(f(4)*(thetha-1)+1)^2/(Nr*(1+4/3*Nr(f(4)*(thetha-1)+1)^3
is very difficult to debug. The first thing I would do define smaller chunks of that expression, starting with terms that repeat frequently. For example, the subexpression
(f(4)*(thetha-1)+1)^3
appears several times, so perhaps define a variable
f4_theta = (f(4)*(thetha-1)+1)^3;
and use it in the longer expression. That will reduce the overall number of parentheses you are using, and make it easier to debug this monster statement.

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