Function used in fsolve with array coefficients

2018 10 21
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更新时间：2018 10 22
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Using fsolve I want to solve an equation for x which has the follwing form:

a1*f1(x)+a2*f2(x)+...+ai*fi(x)=0

where ai are known coefficients (typically read from an inout excel file), i is the index going from 1 to n and fi are some nonlinear functions of x. So the routine to solve for x should look something like this

ai=xlsread('MyFile.xls',1)
Xi=fsolve(@MyFun,X0)  
function MyFun=MyFun(x)
MyFun=...
end

How can I define MyFun knowing that everytime I read a new excel file the number of ai will change?

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Walter Roberson
Walter Roberson 2018-10-21
Do you have access to the Symbolic Toolbox?
Walter Roberson
Walter Roberson 2018-10-21
If the number of ai will change each time, then how are the fi being generated to match the same size?
Saeid
Saeid 2018-10-21
Hi Walter, I have access to the Symbolic Toolbox. As to the fi, the problem is that every time I load the ai from a new excel file there will be a new number of coefficients.
Walter Roberson
Walter Roberson 2018-10-22
You said that the fi are functions. You are reading the ai values in, but not the functions. You have one for each ai value, and you have an indefinite number of ai values. So you must either have a maximum number of ai values and a list of corresponding functions (of which you use the first so-many) or else you must have a way of computing the functions given the index to the function.

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 采纳的回答

Matt J
Matt J 2018-10-22
编辑：Matt J 2018-10-22

0 个投票

You should be passing ai to MyFun. The size of the ai array can be determined inside MyFun, and from that the number of coefficients.
Xi=fsolve(@(x)MyFun(x,ai),X0) ;
function out=MyFun(x,ai)
[m,n]=size(ai);
out=...
end

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