Curve fitting, setting domain/forcing asymptote

Question

Benjamin 2013-5-17

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/76134-curve-fitting-setting-domain-forcing-asymptote

Playing around with data analysis. I have no experience in this area so apologies if I'm asking obvious questions.

I have two data vectors that I want to find the relationship between.

I have with cftool found an exponential function that seems to describe it fairly well. But this function gives a bunch of values outside of my physically possible domain of x-values.

Is it possible to set conditions on the function fitting? For example, I know that y will tend to infinity as x approaches 1 from the right, and y will tend to 0 as x approaches infinity.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Tom Lane 2013-5-17

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/76134-curve-fitting-setting-domain-forcing-asymptote#answer_85840

在 MATLAB Online 中打开

I can't think of a generic way to constrain a function to tend to infinity as x approaches 1, but you might have some luck defining a function that has that behavior and fitting it. For example:

load census                    % define some data having your shape
x = (cdate-1775)/10;
y = 1./pop;
ft = fittype('b1/((x-1)^b2)'); % has the desired asymptotic behavior
f = fit(x,y,ft,'start',[1 1])
plot(x,y,'bx', x,f(x),'r-')    % not a great fit, but it's a start