Need help making a script!!! any help?please

Question

Leonardo Concepcion 2013-11-3

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https://ww2.mathworks.cn/matlabcentral/answers/104771-need-help-making-a-script-any-help-please

编辑： Walter Roberson 2013-11-4

This is the problem to make the scrip: http://i.imgur.com/EkSTC0x.png?1

That is the scrip that someone recommended to me but my professor say that was wrong, and that I have to use the student version of matlab to do it, with the basic thing!!

x_deg = input('Input angle in degrees: ');
x = degtorad(x_deg);
sumTerms = 0;
n = 0;
E = Inf;
while E > 1e-6
    a = ((-1)^n * x^(2 * n + 1)) / factorial(2 * n + 1);
    prevSum = sumTerms;
    sumTerms = sumTerms + a;
    if n ~= 0
        E = abs((sumTerms - prevSum) / prevSum);
    end
    n = n + 1;
end
fprintf('Value of sin(%0.1f) is: %0.5f\n', x_deg, sumTerms

I have the student version, so something in this program is not letting me run the script, But also my professor say that was wrong and that I have to make the program stop when E<=0.000001?

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Walter Roberson 2013-11-3

在 MATLAB Online 中打开

Your professor might want you to structure the loop differently:

while TEST
  ...
end

can be rewritten as

while true
  ...
  if ~TEST; break; end
end

Leonardo Concepcion 2013-11-3

sixwwwwww your code was good, but my prof say that was missing a part, that the program has to stop when E<=0.000001 like it says in the problem.

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Answer 1

Image Analyst 2013-11-3

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https://ww2.mathworks.cn/matlabcentral/answers/104771-need-help-making-a-script-any-help-please#answer_114030

在 MATLAB Online 中打开

degtorad() is not part of base MATLAB. Use x_deg = x * pi/180 instead. Also, take a look at your duplicate question, which has been answered. Here is the corrected code, along with the improved fprintf() that I gave in your original duplicate question (which you ignored for some reason):

clc;
clear all;
x_deg = input('Input angle in degrees: ');
x = x_deg*pi/180
sumTerms = 0;
n = 0;
E = Inf;
while E > 1e-6
    a = ((-1)^n * x^(2 * n + 1)) / factorial(2 * n + 1);
    prevSum = sumTerms;
    sumTerms = sumTerms + a;
    if n ~= 0
        E = abs((sumTerms - prevSum) / prevSum);
    end
    n = n + 1;
end
fprintf('The value of the Taylor series after %d terms is %.7f.\nThe true value of sind(%0.1f) is: %0.7f\n', ...
  n, sumTerms, x_deg, sind(x_deg))

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Image Analyst 2013-11-4

编辑：Image Analyst 2013-11-4

在 MATLAB Online 中打开

Lower than what? Are you inputting a degree (angle) less than the error 1e-6? That would not make sense. So what number did you put in? I entered 45 for 45 degrees. Are you saying that the loop never exits for you and it hangs because you have an infinite loop? That simply cannot be the case. Did you copy and paste my code? Did you step through it with the debugger? For 45 degrees, the error is less than 1e-6 after 5 terms, and the loop exits. How can it not exit on your system?????????

Maybe you're totally thrown off by not understanding how "continue while E is more than 1e-6" is equivalent to "stop looping when E is less than 1e-6". If so, you can put these totally unnecessary lines at the bottom of the while loop, just before the end statement:

if E < 1e-6
  break; % break out of the while loop.
end

but like I said, it's totally unnecessary since the loop will exit anyway when it fails the "while E > 1e-6" test at the top of the loop. But if it makes you feel more secure, then go for it.

If you want to make it keep asking you for angles until you say to quit, then use this code:

n = 0;
while n < 20 % Max number of questions you want to ask
        % This is a failsafe so you don't get into an infinite loop.
  x_deg = input('Input angle in degrees: ');
  x = x_deg*pi/180
  sumTerms = 0;
  E = Inf;
  while E > 1e-6
    a = ((-1)^n * x^(2 * n + 1)) / factorial(2 * n + 1);
    prevSum = sumTerms;
    sumTerms = sumTerms + a;
    if n ~= 0
      E = abs((sumTerms - prevSum) / prevSum);
    end
    n = n + 1;
  end
  fprintf('The value of the Taylor series after %d terms is %.7f.\nThe true value of sind(%0.1f) is: %0.7f\n', ...
    n, sumTerms, x_deg, sind(x_deg))
  promptMessage = sprintf('Do you want to Continue processing,\nor Cancel to abort processing?');
  titleBarCaption = 'Continue?';
  button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
  if strcmpi(button, 'Cancel')
    break;
  end
end

Image Analyst 2013-11-4

You could get rid of the temporary variable "a", but that's about the only way to simplify it.

Let me ask you, when do you think the while loop should quit ? When E < 0.000001? Well that's what it does. Let me ask in a different way. How long do you think the loop should keep going ? Should it keep going while the error is large ? Larger than 0.000001? Well that's what it does. Can you answer those two questions for me?

I hope someone else contributes here to explain it in a different way because I just don't know what else to say to him to make it clear.

Walter Roberson 2013-11-4

编辑：Walter Roberson 2013-11-4

在 MATLAB Online 中打开

Change

fprintf('The value of the Taylor series after %d terms is %.7f.\nThe true value of sind(%0.1f) is: %0.7f\n',

to

fprintf('The value of the Taylor series after %d terms is %012g.\nThe true value of sind(%0.12g) is: %0.12g\n',

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