How do I get the least used character in the text file ?

    a= textread('GreatExpectations.txt','%c');
    [m]=length(a);
    most_used_letter=char(mode(0+a))

[Jan]

Is in 'aba' the 'b' or the 'c' the least used character?

Answer 1

[Mohammad Abouali]

    %Sample text; equivalent to your a
    txt='this is a sample text.';

    uniqueChars=unique(txt(isletter(txt)));
    charCount=arrayfun(@(c) sum(txt==c), uniqueChars);

    % Now printing results
    fprintf('Char   count\n');
    fprintf(' %c     %d\n',[uniqueChars;charCount])

    fprintf('\nThe least Used Characters are:\n')
    fprintf('%c\n',uniqueChars(charCount==min(charCount)))

    fprintf('\nThe most Used Characters are:\n')
    fprintf('%c\n',uniqueChars(charCount==max(charCount)))

Once you run it you well get this:

Char   count
 a     2
 e     2
 h     1
 i     2
 l     1
 m     1
 p     1
 s     3
 t     3
 x     1

The least Used Characters are:
h
l
m
p
x

The most Used Characters are:
s
t

[Tony]

Allah Kheleek , thank you!!

[Mohammad Abouali]

You are welcome.

In larger texts, when you are sure that all characters are used you can remove uniqueChars=unique(txt(isletter(txt))); and then modify the next line form

charCount=arrayfun(@(c) sum(txt==c), uniqueChars);

to

charCount=arrayfun(@(c) sum(txt==c), char([65:90 97:122]));

You have to be sure that all characters are used though. Otherwise, those characters that are not used would be returned as the least used characters.

Also if upper/lower case are not important; then once you are done reading the text file do this:

txt=lower(txt);

and in this case if you decided to use the second form you need char(97:122) instead of char([65:90 97:122]);

If this has answered your question, I appreciate it if you accept the answers.

Answer 2

[per isakson]

Here is a code based on histc

    ffs = 'GreatExpectations.txt';
    fid = fopen( ffs );
    buf = fscanf( fid, '%1c' );  
    fclose( fid );

letters only

    ascii = double( upper( buf ) );
    ascii( ascii<double('A') | ascii>double('Z') ) = [];
    ascii_ranges = ( double('A') : double('Z') );
    [ ascii_counts, ~ ] = histc( ascii, ascii_ranges );
    bar( ascii_ranges, ascii_counts, 'histc' )
    min_val = min( ascii_counts );
    ix_min  = find( ascii_counts == min_val );
    fprintf( 'The letters, %s, each appears %d time(s)\n' ...
        ,   char('A'+ix_min-1), min_val                          )

it prints

    The letters, JQZ, each appears 1 time(s)

&nbsp

Regarding char('A'+ix_min-1) see 'ABC'-'A' Considered Harmful