I keep getting a syntax error on the 'if' function.

function pieulgood
  %approximates and prints pi with Euler's formula
  %called as pieulgood or pieulgood()
  %doesn't return a value, but a print
  true=0;
  n=0;
  while true~=1
    n=n+1;
    for i=1:n
      vec(i)=1/((i)^2);
    end
    approxpi=sqrt(6*sum(vec));
    approxpirounded=str2double(fprintf('.6f\n',approxpi)
    if approxpirounded==pi
      true=1;
    end
  end
  fprintf('A good approximation of pi, by Euler, with n=%d is %.6f\n',n,approxpi)
end

On the line "if approxpirounded==pi", my program tells this,

Please, can someone tell me what syntax is wrong here? I've used 'if' time and time again and never had this problem.

Edit: I fixed my code to coincide with MATLAB

Answer 1

[Steven Lord]

approxpirounded=str2double(fprintf('.6f\n',approxpi)

How many left parentheses ( are on that line? How many right parentheses )? Those numbers should be the same.

[Walter Roberson]

and the output of fprintf is the number of items converted, not the string.

[Jacob Oleshchuk]

thanks, I changed it to a version of round.

Answer 2

[Walter Roberson]

That is not matlab code . matlab does not have endfor or endif or endwhile or endfunction . That appears to be octave code.

Answer 3

[Mark Sherstan]

I may be mistaken but I have not seen this type of syntax used before in MATLAB. Try changing your function to something like this:

function pieulgood
  %approximates and prints pi with Euler's formula
  %called as pieulgood or pieulgood()
  %doesn't return a value, but a print
  n=0;
  
  while 1
    n = n+1;
    for i = 1:n
      vec(i) = 1/((i)^2);
    end
    approxpi = sqrt(6*sum(vec));
    %approxpirounded=str2double(fprintf('.6f\n',approxpi)
    approxpirounded = round(approxpi,6)
    
    if approxpirounded == pi
      break
    end
    
  end
  
  fprintf('A good approximation of pi, by Euler, with n=%d is %.6f\n',n,approxpi)

end

MATLAB stores true as a variable that should not be overwritten so I removed that. Use the round function not fprintf, use end not endif, endwhile, endfunction, etc... Also your function will most likely never end as pi in MATLAB is 3.141592653589793 and you are only comparing 6 decimal places. Please review the code changes and notes I made to gain a better understanding of the problems you are encountering, good job getting on the right track though.

[Jacob Oleshchuk]

is the line

approxpirounded=str2double(fprintf('.6f\n',approxpi)

meant to be a comment?

[Walter Roberson]

yes. the real line is the round afterwards

[Jacob Oleshchuk]

alright, and thanks for the corrections with pi and true. You guys work fast on these and it helps a lot.