Given y, how do I find the value for x?

Question

Will 2013-9-18

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/87512-given-y-how-do-i-find-the-value-for-x

I plotted the function:

x = 0:0.01:2;

y=(1.96./x).*(1-exp(-0.83.*x));

I want to know the x value when y=1. I want to use an interp1 function, but that will only give me y values. Is there a function to find x values?

Also, I can't get my x-axis correct. I want it to span 0-2 (the value I'm looking for is around 1.3) with step sizes of 0.001 (for more precision). Currently, it goes 0 to 200 and I'm at a loss of what to do.

Thanks for the help.

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Answer 1

Andrei Bobrov 2013-9-18

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https://ww2.mathworks.cn/matlabcentral/answers/87512-given-y-how-do-i-find-the-value-for-x#answer_97088

在 MATLAB Online 中打开

>> f2 = @(y)arrayfun(@(y)fzero(@(x)1.96./x.*(1-exp(-0.83.*x))-y,1),y);
>> f2([.03 1 12])
ans = 
       65.333    1.2859   -3.8605

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Will 2013-9-18

Thanks! That gets me the correct answer. However, my matlab understanding is very limited, could you explain a little more how the fzero function and the arrayfun work?

Also, I still have the issue with my x axis being on the wrong order of magnitude.

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