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

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

Answer 1

[Adam Danz]

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

[Jucimar Carpe]

Hi Adam, first of all thank you for you help!

I tried what you said but still not working, the message box doesnt open.

            Sbase_gerador = ~isnan(str2double(strrep((app.potencia.Value),',','.'))); 
       
            
          %  teste_potencia = isa(Sbase_gerador,'double')
            
            if Sbase_gerador==NaN
                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

[Jucimar Carpe]

Sorry, i've made a mistake...

I substitue the NaN by false and it worked!

Thank you!

[Adam Danz]

The correct way,

if ~Sbase_gerado

[Jucimar Carpe]

oh sorry, i've made another mistake, actually is not working, something happens with the data entry and it makes calculate wrong...i am back to same place where i were.

[Adam Danz]

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]

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