MATLAB: Can I use logical indexing to find how many times a character is in a string

charcountlogical indexingMATLABstring

Hi,

I was working on a problem in this MOOC course where I had to count the number of times a character was present in a text file.

While solving the problem, I used a while loop to read each line and just added the length of the array(after using strfind)

like so:

line = fgets(fid);

sum=0;

while ischar(line)

found_in_line = length(strfind(line,character));

sum = sum + found_in_line;

line=fgets(fid);

end

But I tried to just make a sum of a logical array using logical indexing

Like so:

found_in_line = sum(contains(line,character));

But what contains does is just return true if its found in the entire string, I even tried using contains(line(1:end),character)) but this also returns only one logical answer.

Is there a method that I am not aware of which can create a logical array of a character found in a String??

Thank you!

Best Answer

You can perform logical comparisons on a character array (they are not very different from numeric arrays):

str = 'some random text';
nnz(str=='o') % how many 'o' characters
ans = 2

Knowing how to work with arrays is a very powerful approach to using MATLAB.

Related Solutions

MATLAB: How to define string character

It creates a string (character array) containing just a single space character.

MATLAB: ‘strcmp’ works when trying to count number of times a character occurs in a textfile but ‘findstr’ fails!

        s=strfind(oneread,character);%looking for word in each sentence

strfind() returns a list of indices in oneread where the pattern character starts. If no locations are found then strfind() returns empty.

        if isempty(s==0)%checking if s has any elements

s itself can be empty, but it will never contain any 0. In the context of your code, s==0 will be an array of false values the same size as s. Checking isempty() of that would be the same as checking isempty(s)

            c=c+1;

So you are counting the number of times that no matches were found in the line.

Perhaps you intended

        if isempty(s)==0 %checking if s has any elements

which would be the same as

        if ~isempty(s)

in which case you would at least be counting the number of lines that it was found on.

But you are supposed to be checking the count of matches, not the number of lines: if the pattern occurs more than once on the same line, then it should be counted more than once.

If you are intended to count words, then you need to be careful. Suppose you are asked to count 'the' and the text is 'The theoretical theatre theologizes thews." Then the proper answer is either zero ('The' is not 'the') or one (if case distinctions are to be ignored), but you would find four.

Best Answer

Related Solutions

MATLAB: How to define string character

MATLAB: ‘strcmp’ works when trying to count number of times a character occurs in a textfile but ‘findstr’ fails!

Related Question