I have the following string in MATLAB, for example
##%%F1_USA(40)_u
and I want
F1_USA_40__u
Does it has any function for this?
Your best bet is probably regexprep which allows you to replace parts of a string using regular expressions:
s_new = regexprep(regexprep(s, '[()]', '_'), '[^A-Za-z0-9_]', '')
Update: based on your updated comment, this is probably what you want:
s_new = regexprep(regexprep(s, '^[^A-Za-z0-9_]*', ''), '[^A-Za-z0-9_]', '')
or:
s_new = regexprep(regexprep(s, '[^A-Za-z0-9_]', '_'), '^_*', '')
One way to do this is to use the function ISSTRPROP to find the indices of alphanumeric characters and replace or remove the others accordingly:
>> str = '##%%F1_USA(40)_u'; %# Sample string
>> index = isstrprop(str,'alphanum'); %# Find indices of alphanumeric characters
>> str(~index) = '_'; %# Set non-alphanumeric characters to '_'
>> str = str(find(index,1):end) %# Remove any leading '_'
str =
F1_USA_40__u %# Result
If you want to use regular expressions (which can get a little more complicated) then the last suggestion from Tamas will work. However, it can be greatly simplified to the following:
str = regexprep(str,{'\W','^_*'},{'_',''});
Related
How can I go about doing this? So far I've opened the file like this
fileID = fopen('hamlet.txt'.'r');
[A,count] = fscanf(fileID, '%s');
fclose(fileID);
Getting spaces from the file
First, if you want to capture spaces, you'll need to change your format specifier. %s reads only non-whitespace characters.
>> fileID = fopen('space.txt','r');
>> A = fscanf(fileID, '%s');
>> fclose(fileID);
>> A
A = Thistexthasspacesinit.
Instead, we can use %c:
>> fileID = fopen('space.txt','r');
>> A = fscanf(fileID, '%c');
>> fclose(fileID);
>> A
A = This text has spaces in it.
Mapping between characters and values (array indices)
We could create a character array that contains all of the target characters to look for:
search_chars = ['A':'Z', 'a':'z', ',', '.', ' '];
That would work, but to map the character to a position in the array you'd have to do something like:
>> char_pos = find(search_chars == 'q')
char_pos = 43
You could also use containters.Map, but that seems like overkill.
Instead, let's use the ASCII value of each character. For convenience, we'll use only values 1:126 (0 is NUL, and 127 is DEL. We should never encounter either of those.) Converting from characters to their ASCII code is easy:
>> c = 'q'
c = s
>> a = uint8(c) % MATLAB actually does this using double(). Seems wasteful to me.
a = 115
>> c2 = char(a)
c2 = s
Note that by doing this, you're counting characters that are not in your desired list like ! and *. If that's a problem, then use search_chars and figure out how you want to map from characters to indices.
Looping solution
The most intuitive way to count each character is a loop. For each character in A, find its ASCII code and increment the counter array at that index.
char_count = zeros(1, 126);
for current_char = A
c = uint8(current_char);
char_count(c) = char_count(c) + 1;
end
Now you've got an array of counts for each character with ASCII codes from 1 to 126. To find out how many instances of 's' there are, we can just use its ASCII code as an index:
>> char_count(115)
ans = 4
We can even use the character itself as an index:
>> char_count('s')
ans = 4
Vectorized solution
As you can see with that last example, MATLAB's weak typing makes characters and their ASCII codes pretty much equivalent. In fact:
>> 's' == 115
ans = 1
That means that we can use implicit broadcasting and == to create a logical 2D array where L(c,a) == 1 if character c in our string A has an ASCII code of a. Then we can get the count for each ASCII code by summing along the columns.
L = (A.' == [1:126]);
char_count = sum(L, 1);
A one-liner
Just for fun, I'll show one more way to do this: histcounts. This is meant to put values into bins, but as we said before, characters can be treated like values.
char_count = histcounts(uint8(A), 1:126);
There are dozens of other possibilities, for instance you could use the search_chars array and ismember(), but this should be a good starting point.
With [A,count] = fscanf(fileID, '%s'); you'll only count all string letters, doesn't matter which one. You can use regexp here which search for each letter you specify and will put it in a cell array. It consists of fields which contains the indices of your occuring letters. In the end you only sum the number of indices and you have the count for each letter:
fileID = fopen('hamlet.txt'.'r');
A = fscanf(fileID, '%s');
indexCellArray = regexp(A,{'A','B','C','D',... %I'm too lazy to add the other letters now^^
'a','b','c','d',...
','.' '};
letterCount = cellfun(#(x) numel(x),indexCellArray);
fclose(fileID);
Maybe you put the cell array in a struct where you can give fieldnames for the letters, otherwise you might loose track which count belongs to which number.
Maybe there's much easier solution, cause this one is kind of exhausting to put all the letters in the regexp but it works.
A very short question. I have a string
str = 'var(:,1),var(:,2),var(:,3)';
I need to split it with strsplit by ',' but not by ':,' so that I will end up with a cell array
cel = {'var(:,1)','var(:,2)','var(:,3)'};
I am not good with regular expression at all and I tried ,^(:,) but this fails. I thought ^ is not () is group.
How can it be done?
Use a regular expression with negative lookbehind:
cel = regexp(str, '(?<!:),', 'split');
Can some one explain what this line here does? This is part of an old matlab code I need to reuse for my work
matdir = [params.ariens '-' num2str(dirtimes(ii))];
I'm especially confused about the '-' part. Thanks a lot in advance.
Single quotes are used to create a string literal so '-' simply creates a string containing the hyphen character. In MATLAB, [ ... ] performs horizontal concatenation so the line that you have shown concatenates the string stored in params.ariens, the character '-' and the number dirtimes(ii) converted to a string using num2str to creat one long string made up of those three strings.
For example:
c = ['abc', '-', 'def']
% abc-def
class(c)
% char
d = ['abc', '-', num2str(10)]
% abc-10
I have file names stored as follows:
>> allFiles.name
ans =
k-120_knt-500_threshold-0.3_percent-34.57.csv
ans =
k-216_knt-22625_threshold-0.3_percent-33.33.csv
I wish to extract the 4 values from them and store in a cell.
data={};
for k =1:numel(allFiles)
data{k,1}=csvread(allFiles(k).name,1,0);
data{k,2}= %kvalue
data{k,3}= %kntvalue
data{k,4}=%threshold
data{k,5}=%percent
...
end
There's probably a regular expression that can be used to do this, but a simple piece of code would be
data={numel(allFiles),5};
for k =1:numel(allFiles)
data{k,1}=csvread(allFiles(k).name,1,0);
[~,name] = fileparts(allFiles(k).name);
dashIdx = strfind(name,'-'); % find location of dashes
usIdx = strfind(name,'_'); % find location of underscores
data{k,2}= str2double(name(dashIdx(1)+1:usIdx(1)-1)); %kvalue
data{k,3}= str2double(name(dashIdx(2)+1:usIdx(2)-1)); %kntvalue
data{k,4}= str2double(name(dashIdx(3)+1:usIdx(3)-1)); %threshold
data{k,5}= str2double(name(dashIdx(4)+1:end)); %percent
...
end
For efficiency, you might consider using a single matrix to store all the numeric data, and/or a structure (so that you can access the data by name rather than index).
You simply need to tokenize using strtok multiple times (there is more than 1 way to solve this). Someone has a handy matlab script somewhere on the web to tokenize strings into a cell array.
(1) Starting with:
filename = 'k-216_knt-22625_threshold-0.3_percent-33.33.csv'
Use strfind to prune out the extension
r = strfind(filename, '.csv')
filenameWithoutExtension = filename(1:r-1)
This leaves us with:
'k-216_knt-22625_threshold-0.3_percent-33.33'
(2) Then tokenize this:
'k-216_knt-22625_threshold-0.3_percent-33.33'
using '_' . You get the tokens:
'k-216'
'knt-22625'
'threshold-0.3'
'percent-33.33'
(3) Lastly, for each string, tokenize using using '-'. Each second string will be:
'216'
'22625'
'0.3'
'33.33'
And use str2num to convert.
Strategy: strsplit() + str2num().
data={};
for k =1:numel(allFiles)
data{k,1}=csvread(allFiles(k).name,1,0);
words = strsplit( allFiles(k).name(1:(end-4)), '_' );
data{k,2} = str2num(words{1}(2:end));
data{k,3} = str2num(words{2}(4:end));
data{k,4} = str2num(words{3}(10:end));
data{k,5} = str2num(words{4}(8:end));
end
I have a text file that looks like this:
(a (bee (cold down)))
if I load it using
c=textscan(fid,'%s');
I get this:
'(a'
'(bee'
'(cold'
'down)))'
What I would like to get is:
'('
'a'
'('
'bee'
'('
'cold'
'down'
')'
')'
')'
I know I can delimit with '(' and ')' by specifying 'Delimiter' in textscan, but then I will loose this character, which I want to keep.
Thank you in Advance.
The %s specifier indicates that you want Strings, what you want is individual chars. Use %c instead .
c=textscan(fid,'%c');
Update if you want too keep your words intact then you'll want to load your text using the %s specifier. After the text is loaded you can either solve this problem with Regular Expressions (not my forte) or write your own parser then parses each word individually and saves the paranthesis and words to a new cell array.
AFAIK, there is no canned routine capable of preserving arbitrary delimiters.
You'd have to do it yourself:
string = '(a (bee (cold down)))';
bo = string == '(';
bc = string == ')';
sp = string == ' ';
output = cell(nnz(bo|bc|sp)+1,1);
j = 1;
for ii = 1:numel(string)
if bo(ii)
output{j} = '(';
j = j + 1;
elseif bc(ii)
output{j} = ')';
j = j + 1;
elseif sp(ii)
j = j + 1;
else
output{j} = [output{j} string(ii)];
end
end
Which can probably be improved -- the growing character array will prevent the loop from being JIT'ed. The array bc | bo | sp holds all the information to vectorize this thing, I just don't see how at this hour...
Nevertheless, it should give you a place to start.
Matlab has a strtok function similar to C. Its format is:
token = strtok(str)
token = strtok(str, delimiter)
[token, remain] = strtok('str', ...)
there is also a string replace function strrep:
modifiedStr = strrep(origStr, oldSubstr, newSubstr)
What I would do is modify the original string with strrep to add in delimiters, then use strtok. Since you already scanned the string into c:
c = (c,'(','( '); %Add a space after each open paren
c = (c,')',' ) '); % Add a space before and after each close paren
token = zeros(10); preallocate for speed
i = 2;
[token(1), remain] = strtok(c, ' ');
while(remain)
[token(i), remain] = strtok(c, ' ');
i =i + 1;
end
gives you the linear token array of each of the string you requested.
strtok reference: http://www.mathworks.com/help/techdoc/ref/strtok.html
strrep reference: http://www.mathworks.com/help/techdoc/ref/strrep.html