Asked by Daniel
on 26 Jun 2014

I am by no means a Matlab expert so I apologize if this is a question with an easy answer, but I couldn't find any help online.

I have y=x*exp(-(x^2))+x for all x

y is given by previous functions and is some real number

however,x is not yet defined, and I can't get the formula into x= form How can I input this formula without having x defined yet? Is there a way to define x as an empty value and then impute the formula, getting the actual value for x? What am I missing here?

EDIT: I got it to work using fzero. Now I am trying to rework the code to get it to work when y exists as a range of known values instead of one known value. It looks like fzero can't be vectorized, so I tried using a for loop. I get the results, but r0 gts printed into the command line for each value of rm. I want to create a vector of all of the r0 values (and then all of the x0,y0 values). Is this possible?

Here is the code I currently have:

mu=2

nsamples=100;

for rm=linspace(-2,2,10000)

funct=@(r0,rm)mu*r0.*exp(-r0.^2)+r0-rm

options=optimset('Display','off')

[r0]=fzero(@(r0) funct(r0,rm),-2)

end

Answer by José-Luis
on 26 Jun 2014

Edited by José-Luis
on 26 Jun 2014

your_fun = @(x) x.*exp(-(x.^2) ) + x

your_fun(3)

Please accept the answer that best solves your problem.

Daniel
on 27 Jun 2014

Image Analyst
on 27 Jun 2014

You forgot to attach your updated code.

Daniel
on 27 Jun 2014

updated code:

mu=2

nsamples=100;

for rm=linspace(-2,2,10000)

funct=@(r0,rm)mu*r0.*exp(-r0.^2)+r0-rm

options=optimset('Display','off')

[r0]=fzero(@(r0) funct(r0,rm),-2)

end

Also see above

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Answer by Elias Hasle
on 6 Nov 2018

Couldn't you use the symbolic toolbox? E.g.:

syms x_symbol

y = <some expression of x_symbol>

z = <some other expression of x_symbol, could include the y expression etc.>

x_value = 1234

z_result = double(subs(z, x, x_value))

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## Sara (view profile)

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## José-Luis (view profile)

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## Daniel (view profile)

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