How can I make the program count the number of decimals of an inputted amount

withdrawAmount = 0.10
withdrawAmount = 0.1000
S = sprintf('%.99g', withdrawAmount)
S = '0.1000000000000000055511151231257827021181583404541015625'
length(S)
ans = 57

So the number of decimals entered was (57 - length('0.')) --> 55

Can you prove otherwise? NO. The user might have chosen to enter that long string of digits, and the binary value stored in withdrawAmount would be exactly the same.

Furthermore, you used input() . The user might have chosen to respond with (for example)

1/3

Now how many digits did they enter?

Remember that input() with no 's' option executes whatever the user entered as a command . And if the results are floating point, then they are stored in IEEE 754 double precision binary, which does not store values in base 10. You are completely unable to tell whether the user entered 0.1 or 0.10 or 0.10000 or 1/10 when you use input() without the 's' option.

Moral of the story: If you use input() and you need to validate something about the form that the user entered the number, then you need to use the 's' option.

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Tariq Hammoudeh 2021-12-11

编辑：Tariq Hammoudeh 2021-12-11

在 MATLAB Online 中打开

thank you for that but now when i add it to the rest of my code:

decimalPlaces = inf; % variable for the number of decimal places in the entered withdrawal amount
 
%this lets the user enter a different amount if they enter an amount with more than 2 decimal places
while decimalPlaces >= 3 
    withdrawAmountString = input ('Enter amount to Withdraw : ', 's'); %inputed withdrawal amount
    decimalLocation = find(withdrawAmountString == '.', 1, 'last');
    decimalPlaces = length(withdrawAmountString) - decimalLocation;
    if decimalPlaces >= 3
        disp("Please limit your amount to 2 numbers to the right of the decimal point.");
    else
        % if enetered amount has 2 or less decimal places, convert string
        % to a number and contunue.
      withdrawAmount = str2double(withdrawAmountString);
    end
end

while true
    withdrawAmountString = input ('please enter a numeric value : ', 's'); %inputed withdrawal amount
    vetted = regexp(withdrawAmountString, '^([0-9]+(\.[0-9]{0,2})?$)|^\.[0-9]{1,2}$', 'match');
    if ~isempty(vetted)
        withdrawAmount = str2double(vetted);
        break
    end
end
 
%this lets the user enter a different amount if they enter a negative number 
     while withdrawAmount <= 0 
        withdrawAmount= input('invalid amount, please enter a positive number'); 
     end
     
     %this lets the user enter a different amount, if they enter an amount that is more than the ATM's cash reserve
       while withdrawAmount > CR 
           withdrawAmount = input('insufficient funds in ATM, please enter a different amount');
       end

What happens is that, if i start by entering a number < 0 it aslo tells me to "enter a numeric value" instead of "enter a positive value", and also if i start with a number greater than CR i also get "enter a numeric value", and the only way for me to get the correct message for a number greater than CR is only after i either enter a negative number or a letter and the try after that will give me the correct message. so how can i make it give me the correct message for each

Tariq Hammoudeh 2021-12-11

编辑：Walter Roberson 2021-12-12

在 MATLAB Online 中打开

This is all the code related to withdrawing only:

case 1

decimalPlaces = inf; % variable for the number of decimal places in the entered withdrawal amount
 
%this lets the user enter a different amount if they enter an amount with more than 2 decimal places
while decimalPlaces >= 3 
    withdrawAmountString = input ('Enter amount to Withdraw : ', 's'); %inputed withdrawal amount
    decimalLocation = find(withdrawAmountString == '.', 1, 'last');
    decimalPlaces = length(withdrawAmountString) - decimalLocation;
    if decimalPlaces >= 3
        disp("Please limit your amount to 2 numbers to the right of the decimal point.");
    else
        % if enetered amount has 2 or less decimal places, convert string
        % to a number and contunue.
      withdrawAmount = str2double(withdrawAmountString);
    end
end
 
       
       while true
       withdrawAmount = getPositiveNumber();
       if withdrawAmount > CR 
           fprintf('insufficient funds in ATM, please enter a different amount\n');
       else
           break
       end
end
                 
        
       %this lets the user know that they have dont have enough money in their account and lets them enter a different amount 
       while (withdrawAmount + 1.5) > Data.Balance(ac) 
           fprintf( 'INSUFICCIENT FUNDS  Your current balance is : %.2f \n', Data.Balance(ac))
           withdrawAmount = input('Please enter a different amount ');
       end
    
 
        
        %if there are suffiecient funds
        if withdrawAmount + 1.5 <= Data.Balance(ac)
        denominationCount(withdrawAmount); %call function to count the least number of coins and notes.
        
        
        %subtract the withdrawn amount and the service charge from the
        %user's account balance
       Data.Balance(ac)= Data.Balance(ac)-(withdrawAmount + 1.5);
       
       
       writetable(Data, 'NaiveBankData.csv'); %update the csv file with the new balance
       
       %removing the withdrawn amount from the cash reserve
        CR=CR- withdrawAmount;
        
        %write the new cash reserve number into the cash reserve file
        writematrix(CR, reserve);
        
        fprintf('An amount of: %.2f \n has been debited from your account. ', (withdrawAmount + 1.5))
        
        fprintf('  Your remaining balance is: %.2f \n ', Data.Balance(ac))

function posnum = getPositiveNumber()
    prompt1 = 'please enter a numeric value : ';
    prompt2 = 'please enter a positive value : ';
    prev_was_negative = false;
    while true
        if prev_was_negative
            prompt = prompt2;
        else
            prompt = prompt1;
        end
        p = input(prompt, 's');
        vetted = regexp(p, '^(-?[0-9]+(\.[0-9]{0,2})?$)|^-?\.[0-9]{1,2}$', 'match');
        if isempty(vetted)
            prev_was_negative = false;
            % fail to match pattern, do nothing special, loop will repeat
        else
            trial_num = str2double(vetted);
            if trial_num < 0
                prev_was_negative = true;
            elseif ~isnan(trial_num)
                prev_was_negative = false;
                break
            else
              % somehow vetted number converted to nan ??
              fprintf('Bug validating number. Please report input |%s|\n', p)
            end
        end
    end
    posnum = trial_num;
end
 

Walter Roberson 2021-12-12

在 MATLAB Online 中打开

decimalPlaces = inf; % variable for the number of decimal places in the entered withdrawal amount
 
%this lets the user enter a different amount if they enter an amount with more than 2 decimal places
while decimalPlaces >= 3 
    withdrawAmountString = input ('Enter amount to Withdraw : ', 's'); %inputed withdrawal amount
    decimalLocation = find(withdrawAmountString == '.', 1, 'last');
    decimalPlaces = length(withdrawAmountString) - decimalLocation;
    if decimalPlaces >= 3
        disp("Please limit your amount to 2 numbers to the right of the decimal point.");
    else
        % if enetered amount has 2 or less decimal places, convert string
        % to a number and contunue.
      withdrawAmount = str2double(withdrawAmountString);
    end
end

Get rid of that entire section. That section of code should start directly with

    while true
       withdrawAmount = getPositiveNumber();

If you want to specifically tell the user off about having too many decimal places, then edit the getPositiveNumber() function. In particular, you would give that error if

~isempty(regexp(p, '\.[0-9]{3,}'))

which matches a literal period followed by at least 3 digits.

Tariq Hammoudeh 2021-12-12

编辑：Tariq Hammoudeh 2021-12-12

在 MATLAB Online 中打开

Ok i edited it to the following and it does work, it doesnt let me put more than 2 decimal places, but how can i make the 3rd prompt appear when if ~isempty(regexp(p, '\.[0-9]{3,}'))

function posnum = getPositiveNumber()
    prompt1 = 'please enter a numeric amount  : ';
    prompt2 = 'please enter a positive value : ';
    prompt3= 'please limit your amount to  2 decimal places : ';
   
    prev_was_negative = false;
    while true
        if prev_was_negative
            prompt = prompt2;
        else
            prompt = prompt1;
        end
        p = input(prompt, 's');
        vetted = regexp(p, '^(-?[0-9]+(\.[0-9]{0,2})?$)|^-?\.[0-9]{1,2}$', 'match');
        if isempty(vetted)
            prev_was_negative = false;
            % fail to match pattern, do nothing special, loop will repeat
        else
            trial_num = str2double(vetted);
            if trial_num < 0
                prev_was_negative = true;
            elseif ~isnan(trial_num)
                prev_was_negative = false;
                break
            else
              % somehow vetted number converted to nan ??
              fprintf('Bug validating number. Please report input |%s|\n', p)
            end
         if ~isempty(regexp(p, '\.[0-9]{3,}'))
                prev_was_negative = false;
            end
        end
    end
    posnum = trial_num;
end

If you cant answer me its fine, but this is my last issue for my entire program and its done

Walter Roberson 2021-12-13

编辑：Walter Roberson 2021-12-13

在 MATLAB Online 中打开

function posnum = getPositiveNumber()
    prompts = {'please enter a numeric amount  : ',
               'please enter a positive value : ',
               'please limit your amount to  2 decimal places : '};
   
    prompt_num = 1;
    while true
        prompt = prompts{prompt_num};
        p = strtrim(input(prompt, 's'));
        if ~isempty(regexp(p, '\.[0-9]{3,}'))
            prompt_num = 3;
            continue;
        end
        if ~isempty(regexp(p, '^-'))
            prompt_num = 2;
            continue;
        end
        vetted = regexp(p, '^([0-9]+(\.[0-9]{0,2})?$)|^\.[0-9]{1,2}$', 'match');
        if isempty(vetted)
            prompt_num = 1;
            continue;
        end
        trial_num = str2double(vetted);
        if isnan(trial_num)
           fprintf('Bug validating number. Please report input |%s|\n', p);
           prompt_num = 1;
           continue;
        end
        break;
    end
    posnum = trial_num;
end

Tariq Hammoudeh 2021-12-13

thank you that solved it

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Answer 2

Image Analyst 2021-12-9

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1607430-how-can-i-make-the-program-count-the-number-of-decimals-of-an-inputted-amount#answer_851730

在 MATLAB Online 中打开

Try this:

numberOfDecimalPlaces = inf;
while numberOfDecimalPlaces >= 3
    withdrawAmountString = input ('Enter amount to Withdraw : ', 's');
    dotLocation = find(withdrawAmountString == '.', 1, 'last');
    numberOfDecimalPlaces = length(withdrawAmountString) - dotLocation;
    if numberOfDecimalPlaces >= 3
        warningMessage = sprintf('You entered %d numbers to the right of the decimal point.\nPlease use 2 or less.', numberOfDecimalPlaces)
        uiwait(warndlg(warningMessage));
    else
        % Good!  It's 2 or less.  Now convert string to a number.
        withdrawAmount = str2double(withdrawAmountString);
    end
end

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Tariq Hammoudeh 2021-12-10

i tried this but i dont need the warning message, so i changed it to:

decimalPlaces = inf;

while decimalPlaces >= 3

withdrawAmountString = input ('Please limit your entered amount to 2 numbers to the right of the decimal point : ', 's');

dotLocation = find(withdrawAmountString == '.', 1, 'last');

decimalPlaces = length(withdrawAmountString) - dotLocation;

if decimalPlaces >= 3

disp('please limit amount to 2 decimal places')

else

% Good! It's 2 or less. Now convert string to a number.

withdrawAmount = str2double(withdrawAmountString);

end

But the first time i enter a number with 3 decimal places it just displays the message "Please limit your entered amount to 2 numbers to the right of the decimal point" and lets me enter another amount, but the second time i enter a number with 3 decimal places it displays both messages and lets me enter an amount again. So how can i make it so that only the "Please limit your entered amount to 2 numbers to the right of the decimal point" displays each time.

Image Analyst 2021-12-10

在 MATLAB Online 中打开

Sure. You can detect if there is some non-number there like this:

allDigits = all((withdrawAmountString >= '0' & withdrawAmountString <= '9') | withdrawAmountString == '.')
if ~allDigits
    % Tell user they messed up.  
    % Then set numberOfDecimalPlaces = 3 to force it to try again.
    numberOfDecimalPlaces = 3; % Ensure it will ask again.
end

Alternatively you can extract only the digits.

mask = (withdrawAmountString >= '0' & withdrawAmountString <= '9') | withdrawAmountString == '.'
withdrawAmountString(~mask) = []; % Remove non-numbers.

Tariq Hammoudeh 2021-12-11

编辑：Tariq Hammoudeh 2021-12-11

在 MATLAB Online 中打开

The problem with this is that it interferes with another piece of code, my code is:

transactionType= input('1:withdraw 2:deposit 3:account balance 4:end use 5:end program');
 
switch transactionType 
 
    
 %if withdraw chosen   
case 1
    
    
decimalPlaces = inf; % variable for the number of decimal places in the entered withdrawal amount
 
%this lets the user enter a different amount if they enter an amount with more than 2 decimal places
while decimalPlaces >= 3 
    withdrawAmountString = input ('Enter amount to Withdraw : ', 's'); %inputed withdrawal amount
    decimalLocation = find(withdrawAmountString == '.', 1, 'last');
    decimalPlaces = length(withdrawAmountString) - decimalLocation;
    if decimalPlaces >= 3
        disp("Please limit your amount to 2 numbers to the right of the decimal point.");
    else
        % if enetered amount has 2 or less decimal places, convert string
        % to a number and contunue.
      withdrawAmount = str2double(withdrawAmountString);
    end
end
 
 
noLetters = all((withdrawAmountString >= '0' & withdrawAmountString <= '9') | withdrawAmountString == '.');
if ~noLetters
  withdrawAmount=input (' please enter a numeric value')
  numberOfDecimalPlaces = 3;
end
 
     %this lets the user enter a different amount if they enter a negative number 
  while withdrawAmount <= 0 
        withdrawAmount= input('invalid amount, please enter a positive number'); 
     end

the thing with it now is that after i enter a number a number < 0 it also tells me to enter a numeric value, so how can i do it so that it only tells me this after entering a number and not when i enter a negative number

Please note: I changed it to

withdrawAmount= input(please enter numeric data) because when i would enter a letter it takes me back to switch case options instead of letting me directly enter a new number

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Answer 3

David Hill 2021-12-9

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1607430-how-can-i-make-the-program-count-the-number-of-decimals-of-an-inputted-amount#answer_851740

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if you don't care about zeros entered.

x=46.4500000;%if this would be valid
if ~isequal(floor(x*100),x*100)
   'invalid'
end

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Stephen23 2021-12-10

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Sadly this approach fails for many values that could be legitmately described as having only two decimal digits in the fraction part, for example:

x = 0:0.01:10;
y = find(floor(100*x)~=100*x)
y = 1×150
     8    15    29    30    56    57    58    59   110   111   112   113   114   115   116   117   202   204   206   208   219   221   223   225   227   229   231   233   244   246
x(y)
ans = 1×150
    0.0700    0.1400    0.2800    0.2900    0.5500    0.5600    0.5700    0.5800    1.0900    1.1000    1.1100    1.1200    1.1300    1.1400    1.1500    1.1600    2.0100    2.0300    2.0500    2.0700    2.1800    2.2000    2.2200    2.2400    2.2600    2.2800    2.3000    2.3200    2.4300    2.4500

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How can I make the program count the number of decimals of an inputted amount

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How can I make the program count the number of decimals of an inputted amount

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