GUI中的str2num对话框matlab

我正试图纠正这段代码，其中用户将输入a和b的值，但b必须大于a。因此，代码将对其进行测试，在出现错误回复时，会出现一个对话框，询问用户希望重新输入哪个值，用户将单击一个按钮，该按钮将引导他进入另一个对话框，该对话框将询问他a或b的值，然后检查输入的新值。我需要这些值作为数字出来，以便以后进行一些计算，但我无法让我的代码正常工作，以下是我到目前为止得到的结果：

if str2num(b) <= str2num(a); %convert value to doulbe to run the test
    promptMessage = sprintf('The value of the b is smaller or equal to the value of a,     do you want to reinput the value of the a or the value of the b?' );
    button = questdlg(promptMessage, 'Reinput value of a or b ?', 'a', 'b', 'Rod-Crank'); 
    if strcmpi(button, 'a')
        prompt = ('Please reenter the value of a:');
        a=inputdlg(prompt);
        while isnan(str2double(a)) || ~isreal(str2double(a)) || isinf(str2double(a)) ||  str2double(a) <= 0;
            prompt = ('Please reenter the value of a:');
            a=inputdlg(prompt); 
        end
    c = char(a);
    a=str2num(c(1));
    b=str2num(b);

    end
    if strcmpi(button, 'b')
        prompt = ('Please reenter the value of b:');
        b=inputdlg(prompt);
        while isnan(str2double(b)) || ~isreal(str2double(b)) || isinf(str2double(b)) || str2double (b) <= 0;
            prompt = ('Please reenter the value of b:');
            b=inputdlg(prompt); 
        end
     c = char(b);
    b=str2num(c(1));
    a=str2num(a); 
    end
end   
 if isnan(str2double(f)) || ~isreal(str2double(f)) || isinf(str2double(f)) || isempty(f) || str2double (f) < 0; % test if the value of c is valid
     promptMessage = sprintf('The value entered for the Frequency " %0.5g " is incorrect, Please reenter the value for Frequency ', f);
     button = questdlg(promptMessage, 'Error in value of the Frequency.', 'Ok', 'Ok');
end
f = str2num(f);




for t = 0 : 1 : 360;
    Time = t+1;
    O = (2.*pi.*f)./60;
    i = b.^2-a.^2.*((sind(t)).^2);
    j = (a.^2).*(O).*sind(2.*t);

    dt (Time) = a.*cosd(t)+ sqrt(i);
    V (Time) = (-a.*O.*sind(t))-(j/(2.*(sqrt(i))));
    A (Time) = (-a.*(O.^2).*cosd(t))-(4.*(a.^2).*(O.^2).*cosd(2.*t).*i + j.^2)/(4.*(i.^1.5));
    y (Time) = t;
end

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如果str2num（b）出现什么错误消息？在赋值A（I）=b中，b和I中的元素数必须相同。无标题>按钮1_回调（第168行）dt（时间）=a.*cosd（t）+sqrt（i）中出错；gui_mainfcn（第96行）feval（varargin{：}）中出错；无标题（第17行）gui_mainfcn（gui_状态，varargin{：}）中的错误；计算uicontrol回调时@（hObject，eventdata）untitled（'button1_Callback'，hObject，eventdata，guidata（hObject））错误