Can someone tell me why the E (x) (equation below) work perfect up to E (416)? If I try to calculate the E(x) for any x > 416 the answer that I get is NaN.

Question

Oscar 2014-1-29

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/114138-can-someone-tell-me-why-the-e-x-equation-below-work-perfect-up-to-e-416-if-i-try-to-calculate

评论： Matt J 2014-1-29

E=  @(x)1.2840.*(x<=55)+...
    exp(((0.5+((5.9)*((x-55)./(112.3-55)))).^2)./2).*(x>55 & x<=112.3)...
     +24.5325.*(x>112.3);

Thanks for the help.

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

Matt J 2014-1-29

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/114138-can-someone-tell-me-why-the-e-x-equation-below-work-perfect-up-to-e-416-if-i-try-to-calculate#answer_122592

编辑：Matt J 2014-1-29

在 MATLAB Online 中打开

Because for x>416, the expression

exp(((0.5+((5.9)*((x-55)./(112.3-55)))).^2)./2)

evaluates to Inf due to overflow. Then you multiply this Inf by 0 resulting in NaN. To avoid this, you'll need to use if statements to implement each piece of the function instead of implementing as a sum of the different pieces.

2 个评论
显示无隐藏无

Oscar 2014-1-29

Thanks Matt Can you send me a link or example of How to use the if statements to implement each piece of the function?

Matt J 2014-1-29

在 MATLAB Online 中打开

As an alternative to if-statements, you could do this,

function E=Ecalc(x)
   E=nan(size(X));
     idx=(x<=55);
   E(idx)=1.2840;
     idx=(x>55 & x<=112.3);
   E(idx)=exp(((0.5+((5.9)*((x(idx)-55)./(112.3-55)))).^2)./2);
    idx=(x>112.3);
   E(idx)=24.5325;