Finding all visible char in txtfile in MATLAB

Hi everyone,

I have to write a function that counts the number of a certain character in a text file. 2 input arguments are requested: fname (char vector of the filename) and character (the char it counts in the file).

Output argument: the number of characters found. If the file is not found or character is not a valid char, the function return -1.

I wrote a function which passed correctly three of the 4 tests. The wrong one is

==> 1) Test with all visible characters

Explanation: Variable charnum has an incorrect value. When testing with '#' your solution returned -1 which is incorrect. (0)

This is my code:

function charnum = char_counter(fname, character)    
    if isequal(isfile(fname),0)
        charnum = -1;
    else        
        A = fileread(fname);
        char_1 = strfind(A, character);
        charnum = numel(char_1);
        if isequal(exist(fname),0)          
            charnum = -1; 
        elseif isequal(charnum,0)
           charnum = -1;      
        elseif isequal(ischar(char(character)),0)
           charnum = -1;   
        end    
    end
end

Thank you all for your suggestions and advice.

I understand, that I probably should add an instruction to take into account all the characters but I can't find a satisfying way that works. Because when I test for the character '#', it works correctly on my MATLAB: When I test the function with the visible character '#' the answer is correct.

Answer 1

[Walter Roberson]

"or character is not a valid char" is a requirement to test whether the second parameter is datatype char .

Your code is testing isequal(charnum,0) which is testing whether the number of entries found by strfind() is 0, and when it is then you return -1. However, when the input is valid as char data type but does not happen to be found, then input is not an invalid character and so the output should not be -1: the output should be the count, which happens to be 0.

[Morgane Aubineau]

Thank you Walter Roberson. My code isqual... was indeed wrong in that way. But I still can't figure out what to do to pass the "Test with all visible characters". Because when I do it with the grader it's wrong (returns -1 apparently) but sounds right when testing on MATLAB. If I put a text file with "#" as in the example, it returns the number of "#" correctly. It puzzles me. Have you an idea why? Or what can I do to fix it?

[Walter Roberson]

No, if they passed in a character, any character, then as long as the file is found, then you should not be returning -1. -1 is only for the case where the file is not found or the input does not pass ischar() . In all cases where a char was passed in but the char does not happen to occur in the file, then 0 should be returned.

Answer 2

[Gokul surya Subramanian]

if ischar(character)==0
    charnum =-1;
elseif charnum==0
    charnum=0;
    return;
end

Answer 3

[Morgane Aubineau]

I finally solved it like this:

function charnum = char_counter(fname, character)
    if isequal(isfile(fname),0)
        charnum = -1;
    elseif isequal(ischar(character),0)
        charnum = -1;
    else    
        A = fileread(fname);
        characters = char(character);
        char_1 = strfind(A, characters);
        charnum = numel(char_1);

        if isequal(exist(fname),0)
            charnum = -1;
        elseif isequal(charnum,0)
            charnum = 0;
        elseif isequal(ischar(char(character)),0)
            charnum = -1;
        end
    end
end

[Walter Roberson]

It is not necessary to use if isequal(isfile(fname),0) : you could just use if ~isfile(fname)

If isfile(fname) fails, then you never get to the else and so you do not need to test exist(fname) . Likewise, you cannot get to that second ischar() test.