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How to solve an equation using numerical solver in Matlab?

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aa 2020-9-30

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评论： aa 2020-9-30

采纳的回答： Alan Stevens

Hi everyone,

I want to solve this equation using numerical solver. I have value of R and want to calculate the coressponding value of n using numerical solver.

May someone help me here ......

R =1/n^2 [(n+1)ln⁡(n+1)-n]

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Alan Stevens 2020-9-30

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Look up documentation on fzero.

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aa 2020-9-30

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I have no initial point to solve this ....

aa 2020-9-30

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    >> x = fzero(@(x)x^(-2)*((x+1)*ln(x+1)-x)-0.44999)
Error using fzero (line 118)
The input should be either a structure with valid fields or at least two arguments to FZERO.

Alan Stevens 2020-9-30

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Plot a curve of the right hand side Vs n, to see roughly where it equals R.

Alan Stevens 2020-9-30

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You need to supply an initial guess. Also MATLAB use log not ln, for log to the base e.

aa 2020-9-30

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You need to pass the initial guess to fzero as its second argument.

aa 2020-9-30

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see i guess x=5 but still did not get the answer....

Alan Stevens 2020-9-30

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Try

R = 0.44999;
f = @(n) ((n+1).*log(n+1)-n)./n.^2 - R;
n0 = 1; % Initial guess
n = fzero(f,n0);
disp(n)

aa 2020-9-30

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May you help me in generalizing this programme for large number of values. For example, I have more tahn 500 values of R and I want to calculate n for each values of R ....