Is there any way to control the number of decimal places for the outputs?

I am studying root finding problem in numerical analysis. I have written down MATLAB codes for Bisection and Newton methods. They are running fine but I need to have different number of decimal places in the output for different questions. But Matlab either give 4 or 15 decimal places with default and format long settings.

Is there any way to control the number of decimal places in the output through code or by any other mean?

[Mathematics]

For instance, I want to have first column as integers (iteration count) and in the remaining columns I want to have 7 decimal places in the output of the following code (out= [iter, a, b, m, ym, bound]; disp(out)). How can i achieve this? Any suggestion?

f=inline('x.^3-3*x.^2+1'); % 

a=0; b=1; kmax=26; tol=0.00001;

ya=f(a); yb=f(b); 

if sign(ya)== sign(yb), error('function has same sign at end points'), end

disp('step  a  b  m  ym  bound')

for k=1:kmax

      m=(a+b)/2; ym=f(m); iter=k; bound=(b-a)/2; 
      out= [iter,  a,  b,  m,  ym,  bound]; disp(out)
      if abs(ym)<tol, disp('bisection has converged'); break; end
      if sign(ym) ~= sign(ya)
          b=m; yb=ym; 
      else
          a=m; ya=ym; 
      end
      if (iter >= kmax), disp('zero not found to desired tolerance'), end 
  end

Shah

Answer 1

[Matz Johansson Bergström]

I would use num2str(pi,5) to get a string of pi with 5 decimals, for instance.

[Matz Johansson Bergström]

...or you could write something like fprintf(1, 'Approximation: %.5f\n', pi)

[Matz Johansson Bergström]

So, I would put inside the loop

fprintf(1, '%.0f %.7f %.7f %.7f %.7f %.7f\n',iter,a,b,m,ym,bound)

[Mathematics]

Yes, this works nice but I am getting an integer at the end of each row (if I keep \n) or I should say a column of integers as the last column (if I remove \n). It us undesirable, I don't know why it appears and how to get rid of it. Any suggestions?

I am using the following line in my code. out = fprintf(1, '%.0f %.7f %.7f %.7f %.7f %.7f\n',iter,a,b,m,ym,bound); disp(out)

[Matz Johansson Bergström]

Why disp(out)?

[Matz Johansson Bergström]

If you want you could print out 'out' after the loop, I'm not sure you want to see the iterations as they progress, or if you want to see the results after the fact.

Anyway, to do that you need to transpose the 'out' matrix, so we now have

fprintf(1, '%.0f %.7f %.7f %.7f %.7f %.7f\n', out')

Observe, this is AFTER the loop. Additionally, the '\n' is a newline character, you need it.

[Mathematics]

This works fine but shows only the last iteration results. I need to see/print the iterations as they progress i.e. I want to see all iterations on my screen. Would you suggest a fix for this?

Shah

[Mathematics]

It is fixed. I added out= [iter, a, b, m, ym, bound]; fprintf(1, '%.0f %.5f %.5f %.5f %.6f %.6f\n',out') inside the loop and got the desired output form.

Thanks indeed for your valuable suggestions!

Shah