How to solve an equation using numerical solver in Matlab?

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]	

Answer 1

[Alan Stevens]

Look up documentation on fzero.

[aa]

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

[aa]

    >> 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]

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

[Alan Stevens]

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

[aa]

[Alan Stevens]

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

[aa]

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

[Alan Stevens]

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]

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 ....

[John D'Errico]

But what is wrong with writing a loop? Just wrap that code inside a loop, where you change R each time through.

[aa]

Earlier my code did not work with the loop but now I have fixed the error... it works perfectly .. Thanks