Write a function called digit_counter that takes the name of a text file as input and returns the number of digits (i.e., any of the characters, 0-to-9) that the file contains. If there is a problem opening the file, the function returns -1. WARNING:

Hi, I was wondering why this does not work? Do i need to do nested for loops with i and j to traverse through the file ?

function [num] = digit_counter(filename) 
fid = fopen(filename, 'r');
if fid < 0 
    error('error opening file%s\n', filename)
end 
n = fread(fid,1, 'double'); 
dims = fread(fid,n, 'double');
A = fread(fid, 'double'); 
A = reshape(A, dims);
counter = 0 ;
for i = 1 : size(A) 
    if A(i) == 0 || A(i) == 1 ||A(i) == 2 || A(i) == 3 || A(i) == 4 || A(i) == 5 || A(i) == 6 || A(i) == 7 || A(i) == 8 || A(i) == 9 
        counter = counter + 1 ;
    end 
end 
num = counter ; 
fclose(fid) ;
end 

[Emma Sellers]

function [num] = digit_counter(filename) 
fid = fopen(filename, 'r');
if fid < 0 
    error('error opening file%s\n', filename)
end 
n = fread(fid,1, 'double'); 
dims = fread(fid,n, 'double');
A = fread(fid, 'double'); 
A = reshape(A, dims);
[m, n] = size(A);
counter = 0 ;
for j = 1 : n
    for i = 1 : m 
        if A(i,j) == 0 || A(i,j) == 1 ||A(i,j) == 2 || A(i,j) == 3 || A(i,j) == 4 || A(i,j) == 5 || A(i,j) == 6 || A(i,j) == 7 || A(i,j) == 8 || A(i,j) == 9 
        counter = counter + 1 ;
        end 
    end
end 
num = counter ; 
fclose(fid) ;
end 
   

[Rik]

You didn't read the assignment correctly. It tells you that your function should return a -1 when it encounters an error. You are triggering an error instead of returning a -1.

As for the actual solution, I would suggest reading the file as a text file, then figure out how you can count the number of times a specific character occurs, and the sum those counts for the ten characters you need to check.

[Emma Sellers]

function [num] = digit_counter(filename) 
fid = fopen(filename, 'r');
if fid < 0 
   num = -1 ; 
else 
A = fprintf(fid,'%4.4f\n',filename);
[m, n] = size(A);
counter = 0 ;
for j = 1 : n
    for i = 1 : m 
        if A(i,j) == 0 || A(i,j) == 1 ||A(i,j) == 2 || A(i,j) == 3 || A(i,j) == 4 || A(i,j) == 5 || A(i,j) == 6 || A(i,j) == 7 || A(i,j) == 8 || A(i,j) == 9 
        counter = counter + 1 ;
        end 
    end
end
num = counter ; 
fclose(fid) ;
end 

[Emma Sellers]

Something more like this?? I still am getting an error.

Answer 1

[Stephen23]

This should get you started:

function num = digit_counter(fnm) 
fid = fopen(fnm,'rt');
if fid<3
    num = -1;
else
    vec = fread(fid,[1,Inf],'char');
    fclose(fid);
    num = nnz(isstrprop(char(vec),'digit'));
end
end

[Rik]

Or, keeping more of your original code, you can do something like this:

function [num] = digit_counter(filename) 
fid = fopen(filename, 'r');
if fid < 0 
   num = -1 ;
   return
end
A = fscanf(fid,'%s');
[m, n] = size(A);
counter = 0 ;
for j = 1 : n
    for i = 1 : m 
        if A(i,j) == '0' || A(i,j) == '1' ||A(i,j) == '2' || ...
                A(i,j) == '3' || A(i,j) == '4' || A(i,j) == '5' || ...
                A(i,j) == '6' || A(i,j) == '7' || A(i,j) == '8' || A(i,j) == '9' 
        counter = counter + 1 ;
        end 
    end
end
num = counter ; 
fclose(fid) ;
end 

[Stephen23]

Won't the fscanf '%s' format stop at the first whitespace?

[Emma Sellers]

That works! Thank you! So when I searched for "reading files" in matlab, it came up with the function fprintf, why? That was the only thing I was missing.

[Rik]

I noticed in the doc that it is used to create example files to later read with another function.

[Rik]

@Stephen, it does. I didn't test the code, so I needed to re-read the doc to confirm that it ignores white-space (and probably stops when it sees it).

I currently tend to use my own readfile function, which uses fileread on Matlab and fgetl on Octave. That odd choice of functions has more to do with the difficulty of detecting the encoding, as well as keeping a wide range of compatible releases, but it has so far worked on my test cases.