Counting characters in a file
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Hussain Bhavnagarwala
am 28 Mär. 2020
Kommentiert: Walter Roberson
am 4 Sep. 2022
Hello,
I am doing an online course on matlab in coursera and I have come a cross a problem that seems hard for me to solve.
I need to write a function that takes the name of the text file and a paticular charater as input and then the function must count how many times the character is present in the file and return that number.
function charnum = char_counter(b,a)
fid = fopen(b,'r');
if fid < 0 || ~ischar(a) || length(a) == 0
charnum = -1;
return
end
t=0;
d=1;
while (d>0)
d = fgetl(fid);
x = strfind(d,a);
t = t + length(x);
end
charnum = t;
fclose(fid);
end
I have passed 3 out of 4 checks, following is the error that I am getting
Variable charnum has an incorrect value. When testing with ' ' your solution returned 1 which is incorrect. (75444).
I tried countin the number of " ' ' " as well and it seemed correct to,
I would like to the mistake that I am making.
Thanks
Hussain
6 Kommentare
Image Analyst
am 29 Mär. 2020
Adam, I'd put that down in the answer section so you can get credit for it. I was about to say the same thing.
Akzeptierte Antwort
Adam Danz
am 29 Mär. 2020
Bearbeitet: Adam Danz
am 30 Mär. 2020
Here's a demo to count the instances of a character in a text file.
This demo searches for a space character ' ' and then replaces the space characters with squares so you can visually confirm the results.
This is the simple text file I'm reading in (also attached).
Read in the file and count the empty spaces ' '
idx shows the location of spaces.
c = fileread('myTextFile.txt');
idx = c == ' ';
sum(idx)
% ans =
% 67
To search for a case insensitive character, use upper() or lower().
idx = lower(c) == 'a';
Replace the spaces with squares
cCopy = c;
cCopy(idx) = char(746); % square character
disp(cCopy)
Spaces have been replaced with squares. Number of squares = 67
11 Kommentare
Ameer Hamza
am 30 Mär. 2020
The condition lower(f) == lower(a) should be carefully used. It is only valid for case-insensitive counting of characters.
Adam Danz
am 30 Mär. 2020
Bearbeitet: Adam Danz
am 30 Mär. 2020
f = lower(fileread(b));
charnum = sum(f=='a');
which indicates a case insensitive search. There's no use in doing that unless the search key is also case insensitive. But it's good to explicitly point that out for the OP.
With an empty space search, case doesn't matter since upper(' ')==lower(' ').
Weitere Antworten (3)
Rishi Diwan
am 23 Mai 2020
function charnum = char_counter(fname,character)
fid = fopen(fname,'rt');
if fid <= 0 || ~ischar(character) || ~ischar(fname) || length(fname)==0 || length(character)==0 || isempty(fname) || isempty(character)
charnum=-1;
return;
end
c=0;
ol=fgets(fid);
while ischar(ol)
c=c+count(ol,character);
ol=fgets(fid);
end
charnum=c;
fclose(fid);
end
3 Kommentare
yi yang
am 4 Sep. 2022
a shorter version of your code:
function charnum = char_counter(fname,character)
charnum = count(fileread(fname),character);
end
Walter Roberson
am 4 Sep. 2022
This turns out to be a homework assignment. The checks for file existing and for the input being a valid character are required as part of the assignment.
Ahsiur Rahman Nirjhar
am 24 Mai 2020
function x=char_counter(a,b)
fid=fopen(a,'rt');
if fid <0 || ~ischar(b)
s=-1;
else
s=0;
oneline=fgets(fid);
while ischar(oneline)
s=s+sum(double(oneline)==double(b));
oneline=fgets(fid);
end
fclose(fid);
end
x=s;
0 Kommentare
Mert Yalcinoz
am 1 Feb. 2022
By looking other's people answers i have combined my code and got the result.
function charnum=char_counter(fname,character) %creating function
fid=fopen(fname,'rt');
if fid<0 || ~ischar(character) || length(character)==0 %conditions
charnum=-1;
return
end
a=0; %setting a total value for found desired string
b=fgets(fid); %for reading the first line, returns single line in a string
while ischar(b) %loop for each line
a=a+count(b,character); %summing when a character is found
b=fgets(fid); %if there is no new line, b becomes -1 and loop ends.
end
charnum=a; %setting output variable
fclose(fid);
end
1 Kommentar
Walter Roberson
am 1 Feb. 2022
Suppose that a valid file name is passed in, but suppose that character is not a valid character or is empty. Then you set charnum=-1 and return... without having closed the file.
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