how to plot this data as data-points?

Question

Otto 2012-11-5

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/52833-how-to-plot-this-data-as-data-points

Hi All,

I have written a code to estimate a root of x^10=1 using modified regula falsi. My code is working pretty well now but I want to plot ea versus iter variable and xr versus iter variable as data-points but there is a problem about this. In my workspace, iter,ea and xr appear only as their last values. I want to see their previous values too. Because of this I can't plot a data-point figure point by point.

Here is my code;

f=@(x)x^10-1;
xl=0;
xu=1.3;
xr = xu;
es=0.01;
fl=f(xl);
fu=f(xu);
iter=0;
iu = 0; 
il = 0;
fprintf('\n\n%10s\t%10s\t%10s\t%10s\t%10s\t%10s\t\t%10s\t%10s\n',...
        'iter','xl','xu','f(xl)','f(xu)','xr','f(xr)','ea')
fprintf(['      ',repmat('-',1,92),'\n'])    
while 1
    xrold = xr;
    xr = xu - fu*(xl-xu)/(fl-fu);
      fr = f(xr);
      iter=iter+1;
      if xr<0
      elseif xr>0
          ea=abs((xr-xrold)/xr)*100;
      end
      test = fl*fr;
      if test<0
          xu = xr;
          fu = f(xu);
          iu = 0;
          il = il+1;
          if il>=2
              fl=fl/2;
          end
      elseif test>0
          xl=xr;
          fl=f(xl);
          il=0;
          iu=iu+1;
          if iu>=2
              fu=fu/2;
          end
      else
          ea=0;
      end
      if ea<es
          break
      end
      fprintf('%10.2i\t%10.7f\t%10.7f\t%10.7f\t%10.7f\t%10.10f\t%10.7f\t%10.4f\t\n',...
              iter,xl,xu,f(xl),f(xu),xr,f(xr),ea)
end
fprintf('\n\n')
ModFalsePos=xr;

What would you recommend for this situation?

I'll appreciate for any help.

Thanks Already!

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Otto 2012-11-6

Anyone to solve this problem?

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Answer 1

Walter Roberson 2012-11-6

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/52833-how-to-plot-this-data-as-data-points#answer_64449

在 MATLAB Online 中打开

In the loop, before the "end",

saved_iter(iter) = iter;
saved_ea(iter) = ea;
saved_xr(iter) = xr;

Then after the loop, you can plot saved_iter vs saved_ea and so on.

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Otto 2012-11-6

Thanks for your help, I have a last question. With this code, I can see the iterations between number 01 and number 11 but I want to see the initial values,i.e 00'th iteration, and the final iteration, ie 12'th iteration, how can I do this? what would you recommend for that? I have only 1 hour to complete this project, so time is running out, I will appreciate for any help. Thank you again!

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