Doubt regarding the fzero command.

Hi guys,

What does it mean when we write in a code P0 = fzero (@somefunction, [1, 25]). Does it mean search for an answer in the interval from 1 to 25 ? I usually set one value in which fzero start its search for the solution.

That`s the actual line that`s puzzling me

P0=fzero(@(P0) estimateSurfacePressure(P0,false,extPar), [1 25]);

The last thing is estimateSurfacePressure is a .m file the way fzero goes in this file is pretty weird for me. What does @(P0) mean? It looks somewhat like those function we create like this y = @(x) [x^2] is there something to do with it?

Thank you very much for helping.

Answer 1

[José-Luis]

It means that the function estimateSurfacePressure() is in the path and will be evaluated for different values of PO until one yielding zero value has been found.

It also means that estimateSurfacePressure() returns a scalar.

[Douglas Alves]

but why is it written like

P0=fzero(@(P0) estimateSurfacePressure(P0,false,extPar), [1 25]);

I would've written as

P0=fzero(estimateSurfacePressure(P0,false,extPar), [1 25]);

what's the @(P0) for ? I know that @ calls functions but this file is not actually an actual function such as y=@(x) [x^2] ;

and is it right that P0 will be varied until I have an answer but in the range [1,25] ?

Thank you Jose.

[José-Luis]

Yes, it will look for an answer in the [1 25] interval.

fzero() takes a scalar-valued function handle as first argument. estimateSurfacePressure() takes three arguments but the author of the code only wanted to find the roots when one of them varies. Therefore he uses a function handle that allows him to let only P0 vary.

With the @ you are creating an anonymous function, that takes only one argument: P0 and is then passed to fzero().

Please read the documentation of function handles for further information.