Testing if a input is a numerical (double) of character

Question

Jucimar Carpe 2019-8-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/476603-testing-if-a-input-is-a-numerical-double-of-character

评论： Jucimar Carpe 2019-8-18

Hi folks, i'm implementing a software on appDesigner and i want to prevent wrong entries from users.

I've tried to use the folowing code but it's not working. My gol would be, check if the user entered with a number or character. If it's a number then OK, otherwise open a warning dialog box informing the error and then stop the program.

The way i've writed it's not working.

 Sbase_gerador = str2double(strrep((app.potencia.Value),',','.'));% Read entry data and convert comma to '.' if needed
            
            teste_potencia = isnumeric(Sbase_gerador)
            if teste_potencia==0
                opts= struct('WindowStyle','modal','Interpreter','tex');
                tensao_incorreta_t2 = warndlg('\fontsize{11}Caracteres diferentes de números não são aceitos.',...
                    'Entrada incorreta de dados', opts);
                app.potencia.Value='0';
            end

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Answer 1

Adam Danz 2019-8-18

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https://ww2.mathworks.cn/matlabcentral/answers/476603-testing-if-a-input-is-a-numerical-double-of-character#answer_388089

编辑：Adam Danz 2019-8-18

在 MATLAB Online 中打开

You can use str2double() to convert the string to numeric. If the string did not contain something that can be converted to numeric, it will return NaN.

isNumber = ~isnan(str2double(str));

Examples

isNumber = ~isnan(str2double('100'))            % true
isNumber = ~isnan(str2double(' 100 '))          % true
isNumber = ~isnan(str2double('3.1415926'))      % true
isNumber = ~isnan(str2double('8.3205e+24'))     % true
isNumber = ~isnan(str2double('Abcd'))           % false
isNumber = ~isnan(str2double('5 and 7'))        % false

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Adam Danz 2019-8-18

Do you mean a certain input is not producing the expected output with the code from my answer? Or is there a different problem?

Jucimar Carpe 2019-8-18

在 MATLAB Online 中打开

I let in this way.

It seems the instruction ~isnan let the variable Sbase_gerador with some random number (that i dont know what it is) because of the logical answer. And this make my calculations crazy.

          
            Sbase_gerador = ~isnan(str2double(strrep((app.potencia.Value),',','.')))
            
            if ~Sbase_gerador
                opts= struct('WindowStyle','modal','Interpreter','tex');
                potencia_incorreta = warndlg('\fontsize{11}Caracteres diferentes de números não são aceitos.',...
                    'Entrada incorreta de dados', opts);
                app.potencia.Value='0';
            end