Undefined function or variable Matlab

Question

I need to write a fixed point iteration algorithm and it's mostly coded but I'm running into this error:

Undefined function or variable 'g'.

I want to define g as g(x) = 1/2*(1+5/x). However, I'm a matlab n00b and unsure how to do this. Any help would be much appreciated, thanks.

  function [y,k] = fixedpoint(g,p0,tol,max1)
          for k=1:max1
          p = g(p0);
          err = abs(p-p0);
          abserr = abs(sqrt(5)-p);
          ratioerr = abserr/(abs(sqrt(5)-p0));

          if (err<tol)
             break
          end
          p0 = p;

  end
  if (k==max1)
      disp('The algorithm did not converge')
  end
  y = p;

BenMorel · Accepted Answer · 2013-12-31 12:05:48Z

3

You can define g as a anonymous function

g = @(x)1/2*(1+5/x)

Then call your function fixedpoint in usual way

edited Dec 31, 2013 at 12:05

BenMorel

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answered Sep 21, 2013 at 22:16

P0W

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2 Comments

chappjc Over a year ago

You can also pass the handle to a M file function by passing @funcname.

user85109 Over a year ago

Be VEWY, VEWY careful following this advice. Note that the code P0W shows uses / not ./ so if called with vector or array input, it will produce totally unexpected results. Then you next anguished question will be to ask why your code does not work. Far better programming technique is to use ./ on things like this, even if you normally expect to pass it scalar input, because one day you won't do so.

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