求lscurvefit的程序语句解释

open lscurvefit函数如下：%
------------Initialization----------------defaultopt = struct(...
'Algorithm','trust-region-reflective',...
'DerivativeCheck','off',... 'Diagnostics','off',...
'DiffMaxChange',1e-1,... 'DiffMinChange',1e-8,...
'Display','final',... 'FunValCheck','off',...
'Jacobian','off',... 'JacobMult',[],... % JacobMult set to [] by
default 'JacobPattern','sparse(ones(Jrows,Jcols))',...
'LargeScale','on',... 'LevenbergMarquardt','on',...
'LineSearchType','quadcubic',... 'MaxFunEvals',[],...
'MaxIter',400,...
'MaxPCGIter','max(1,floor(numberOfVariables/2))',...
'OutputFcn',[],... 'PlotFcns',[],...
'PrecondBandWidth',Inf,... 'ScaleProblem','none',...
'TolFun',1e-6,... 'TolPCG',0.1,... 'TolX',1e-6,...
'TypicalX','ones(numberOfVariables,1)');% If just 'defaults' passed in,
return the default options in Xif nargin==1 && nargout <= 1
&& isequal(FUN,'defaults') x = defaultopt;
returnendif nargin < 7 options = []; if nargin <
6 UB = []; if nargin < 5 LB = [];
end endendproblemInput = false;if nargin == 1
if isa(FUN,'struct') problemInput = true;
[FUN,x,XDATA,YDATA,LB,UB,options] = separateOptimStruct(FUN); else %
Single input and non-structure.
error('optim:lsqcurvefit:InputArg',['The input to LSQCURVEFIT should be
either a ',... 'structure with valid fields or consist of at
least four arguments.']); endendif nargin < 4 &&
~problemInput error('optim:lsqcurvefit:NotEnoughInputs', ...
'LSQCURVEFIT requires four input arguments.');endif nargout >
5 computeLambda = 1;else computeLambda = 0;endcaller =
'lsqcurvefit';[x,Resnorm,FVAL,EXITFLAG,OUTPUT,LAMBDA,JACOB] = ...
lsqncommon(FUN,x,XDATA,YDATA,LB,UB,options,defaultopt,caller,... computeLambda,varargin{:});请问这段程序每句话都代表什么意思？那句是赋初值，哪句是代表迭代步长？哪句是修改我赋的初值的？一团乱麻，搞不明白，不知道哪句是哪句，就高手指点，非常感谢请问这个程序是用什么方法迭代的，从程序中的那部分可以看出来？从程序中的那部分可以看出它是向着哪个方向修改步长的？

OMG，忘了修改空格了，乱套了

哇。都是什么东东。。