0 个投票

Here are my codes, I keep getting wrong feedback which drive me crazy! Here's the problem: Basicly the problem is to solve a nonlinear equation by using the fzero command. The function is Φ（r)=[Φ0*e^-r/delta]/(4*pi*D*r) And solve r when Φ（r)/Φ0=10% Every parameters are in the command
My problem is: Index exceeds matrix dimensions.
Error in YZHW61 (line 47) fprintf(' %6.3f %2u %6.2f %+6.2E \n',...
%%YZHW61
%Find the distance away from the point source of laser
%
%Written 2/11/2012 by YZ
%Last updated 2/11/2012 by YZ
%
%First list parameters
%μs’=μs（1-g)=10cm-1
%μt’=μa+μs’=10.1cm-1
%D=（1/3）*μt’=3.37cm-1
%δ=sqrt（D/μa）=5.8
%So the final equation becomes Φ(r)=(Φ0*e^(-r/5.8))/(4*pi*3.37*r)
%Simplify the equation and we get:
%Φ=(e^(-r/5.8))/13.48*pi*r where Φ(Phi)=Φ(r)/Φ0 that represents the
%percentage of the new light intensity compared to the original
%light intensity
date
clear all
%First plot Diffusion Equation for r between 0.5 and 100
for i=1:1:200; %loop counters musht be be nonzero,positive integers
r=i/2; %this will give us 0.5cm distance
press(i)=r;
g=0.9;
mius=100;
miua=0.1;
mius1=mius*(1-g);
miut1=miua+mius1;
D=(1/3)*miut1;
delta=sqrt(D/miua);
P(i)=exp(-r/delta)/(4*pi*D*r)*100;
end
hold on
plot(press,P);axis equal; grid
%
% Get user input for the light fluence rate(percentage)
%We need to pass this information to the function by using the global
%variable
global Phi
Phi=0.1;
%
%Choose initial guess
distance=1;
[r,error,exitflag,output]=fzero(@Diffusion,distance);
%
%What's the solution, how many iterations, what's the error?
fprintf=('distance (Iterations fluence rate error) \n');
fprintf(' %6.3f %2u %6.2f %+6.2E \n',...
r, output.funcCount, Phi, error)
plot(r,0.1,'o')
And here is my function:
function Pest=Diffusion(distance)
%Diffusion equation for distance r
%
%First written by YZ on 2/11/2012
%Last updated by YZ on 2/11/2012
%
global Phi
g=0.9;
mius=100;
miua=0.1;
mius1=mius*(1-g);
miut1=miua+mius1;
D=(1/3)*miut1;
delta=sqrt(D/miua);
Pest=exp(-distance/delta)/(4*pi*D*distance)*100-Phi;
end
Really appreicate anyone who can help me!

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Walter Roberson
Walter Roberson 2012-2-12
What problem are you encountering? There is nothing in your source that an on-looker would clearly understand to be "feedback", and you have not mentioned any error message.
Yu
Yu 2012-2-12
I'm so sorry, please see the edited verision.

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 采纳的回答

Image Analyst
Image Analyst 2012-2-12

0 个投票

Several errors in your code. The big one is this line:
fprintf=('distance (Iterations fluence rate error) \n');
You are not allowed to have an equal sign after fprintf(). I think what you did was to essentially overwrite fprintf with a character string. Then in the next line you tried to access some element of the string beyond the end of it.
Secondly, you are overwriting error(). DON'T DO THAT! It's a built in function. Use "errorStructure" as the name instead of "error".
[r,errorStructure,exitflag,output]=fzero(@Diffusion,distance);

9 个评论
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Yu
Yu 2012-2-12
Thank you for your answer, however, I changed r from 0.005 to 1 and changed the initial guess to 0.005 due to my understand and graph to the function; but then I encountered a new problem: too many output arguments.It that because I choos the wrong initial guess? Because I changed to different values and still get the same mistake.
Image Analyst
Image Analyst 2012-2-12
I don't care at all about those. Did you change what I said to change? Did you remove the equal sign and rename error to errorStructure?
Yu
Yu 2012-2-12
I did; actually the changes are made after I did what you want me to change.
Image Analyst
Image Analyst 2012-2-12
I don't see how r was ever .005. I see that it was r=i/2. Where does it now equal 1? Also, what line said that some function had too many output arguments? It helps if you paste the error.
Yu
Yu 2012-2-12
Error using error
Too many output arguments.
Error in YZHW61 (line 47)
fprintf(' %6.3f %2u %6.2f %+6.2E \n',...
This is my error.
And I set r range from 0.005 to 1; because i have to be nonzero and positive figures so I let r=i/200 to get the range of r.
for i=1:1:200; %loop counters musht be be nonzero,positive integers
r=i/200; %this will give us 0.005 distance
Image Analyst
Image Analyst 2012-2-12
Doesn't make sense. You're not using "error" anymore, remember? I told you to change it to "errorStructure" and you said you did.
Yu
Yu 2012-2-12
distance=0.005;
[r,errorStructure,exitflag,output]=fzero(@Diffusion,distance);
This is what I did according to your suggestion.
Yu
Yu 2012-2-12
Got it, thank you so much !
Image Analyst
Image Analyst 2012-2-12
I guess you also eventually remembered to change it in the fprintf() also.

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