Question

我有一些图像文件。我正在尝试使用每个文件执行一些计算，如果满足特定条件，我想回到代码中的特定行，然后从那里再次运行它。但是只有一次。不管第二次是否满足if条件，我都想转到下一个迭代。但是，MATLAB似乎没有goto函数，而且，使用goto隐含错误的编程，所以我认为我会针对满足if条件的特定“ i”值对for循环进行两次迭代。

file = dir('*.jpg');
n = length(file);
for i = 1:n
    *perform some operations on the 'i'th file*
    if 'condition'
        *run the for loop again for the 'i'th file instead of going to the 'i+1'th file*
         i=i-1;
    else
        *go to next iteration*
    end
end

我试图通过将循环内的循环变量'i'更改为'i-1'进行编码，以便在下一次迭代中，将再次重复'i'个循环，但这样做给出了错误的信息输出，尽管我不知道代码中是否还有其他错误，或者内部更改循环变量是否是问题的原因。对此有任何帮助。

Answer 1

将for循环替换为while循环，以提高灵活性。唯一的区别是您必须手动递增i，因此这也使您不必递增i。

鉴于您的新要求，您可以跟踪尝试次数，并在需要时轻松更改此尝试：

file = dir('*.jpg');
n = length(file);

i = 1;
attempts = 1; 

while i <= n
    % perform code on i'th file
    success =  doSomething(); % set success true or false;

    if success
        % increment to go to next file
        i = i + 1;

    elseif ~success && attempts <= 2 % failed, but gave it only one try
        % increment number of attempts, to prevent performing 
        attempts = attempts + 1;
    else % failed, and max attempts reached, increment to go to next file
        i = i + 1;
        % reset number of attempts 
        attempts = 1;
    end
end

Answer 2

鉴于在rinkert's answer之后添加的新要求，最简单的方法是在单独的函数中将代码与循环分离：

function main_function

  file = dir('*.jpg');
  n = length(file);
  for i = 1:n
    some_operations(i);
    if 'condition'
      some_operations(i);
    end
  end

  function some_operations(i)
    % Here you can access file(i), since this function has access to the variables defined in main_function
    *perform some operations on the 'i'th file*
  end

end % This one is important, it makes some_operations part of main_function

如果满足if条件，如何跳至for循环中的特定位置？

2 个答案: