fsolve accuracy

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John Mulvihill
John Mulvihill 2011-11-17
评论： John Mulvihill 2014-4-24
Hi all,
I am fairly new to matlab so excuse my ignorance as this could be an easy problem.
I am using the fsolve function and it is working fine and it outputs my three parameters that I need. However all three numbers are limited to an accuracy of four decimal places which I would like to increase to 6 or even more.
Does anyone have any advice to help me improve the accuracy? This is a snapshot of the code...
Init_Guess = [0.05 0.02 0.0000406];
options=optimset('Display','iter','MaxIter',3000,'MaxFunEvals',3000, 'TolFun', 1.0e-12, 'TolX',1.0e-12);
Coeffs = fsolve(@Solution_1,Init_Guess,options)
As you can see with the Initial guess I am trying to force the code to increase the decimal places but it doesn't seem to want to do it.
Regards
John Mulvihill

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采纳的回答

the cyclist
the cyclist 2011-11-17
My guess is that you are talking about what is displayed, as opposed to what is calculated. Try typing
>> format long
to see more digits in the output of the command window.

更多回答（1 个）

Mahyar
Mahyar 2014-4-24
I have same problem too, and tried format long but it does not have any effect of the meaningful digits of results. Am I wrong?!
  1 个评论
John Mulvihill
John Mulvihill 2014-4-24
Hey Mahyar,
This answer from the cyclist solved it for me from what I remember! When I run the "fsolve" function in my code it calls on another .m file (Solution_1 from the example I gave) and within this file I have placed "format long" just after the "function" line which gives me 15 decimal places answers.
Example of Solution_1 file:
function Cost = Solution_1(Init_Guess)
format long
C1 = Init_Guess(1); C2 = Init_Guess(2); % these are the answers I want for whatever equation I put in
Cost = sum(C1 - C2) % this doesn't matter
end
The answer I get from this looks like the folllowing:
C1 = 0.008198986069043 and C2 = 0.005224578396002
Hope this helps
John

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