MATLAB Answers

Not Converting ASCII to DECIMAL

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Elliot Alderson
Elliot Alderson on 23 Nov 2019
Commented: the cyclist on 24 Nov 2019
I have converted decimal number to ASCII, however I cannot turn the same ASCII code back to it's decimal.
Here is the code:
%DECIMAL TO ASCII
a = 1;
%dec2bin(a); % decimal to binary conversion
b = double(num2str(a)); % decimal to ASCII conversion
%OP TO ASCII
%ASCII TO DECIMAL
c= str2double(b); %ISSUE
d=str2num(b); %ISSUE

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Answers (2)

the cyclist
the cyclist on 23 Nov 2019
c = b-'0'

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Elliot Alderson
Elliot Alderson on 24 Nov 2019
This solves the issue that I'm having, but how is it working?
the cyclist
the cyclist on 24 Nov 2019
I poked around for some specific documentation on this behavior, but didn't find it.
I believe what is happening is that MATLAB converts the character array, so the above is equivalent to
c = b - double('0')

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per isakson
per isakson on 23 Nov 2019
Edited: per isakson on 24 Nov 2019
I guess the problem is in the meaning of "Converting ASCII to DECIMAL".
The character '1' is represented by the decimal ascci number 49.
The function double() converts from character to decimal ascci number
>> double('1')
ans =
49
and char() converts from decimal ascci number to character
>> char(49)
ans =
'1'
str2double() and num2str() are something else. Look them up in the documentation.
>> str2double('1')
ans =
1
>>
>> num2str( 1 )
ans =
'1'
>>

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Elliot Alderson
Elliot Alderson on 24 Nov 2019
I understand your first line of code, but the current issue that I have is that I take the decimal number from the user, but I am having trouble converting that number to ascii. For example:
n1=input('Enter n1: ');
a=double(n1);
would not give me the ascii of said number, the double would be the same, since I'd be putting interger values in there in the first place. Whereas If I write a like:
a=double('n1');
This would only convert the characters 'n' and '1' into ASCII, not the user input.
per isakson
per isakson on 24 Nov 2019
Run and answer with the keystrokes "1" and "Enter"
%%
n1=input('Enter n1: ');
class( n1 )
the output in the Command Window will be
Enter n1: 1
ans =
'double'
Thus, n1 returned by input() is already double. Matlab is smart enough to understand that the user wants a double :(
Run and answer with the keystrokes "1" and "Enter"
n1=input('Enter n1: ', 's' ); % notice the 's'
class( n1 )
the output in the Command Window is now
Enter n1: 1
ans =
'char'
The 's' forces input() to return characters and thus
a=double(n1)
returns decimal ascii numbers
a =
49

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