Reading a text file and rows with data

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Damith
Damith 2016-6-14
回答： Shameer Parmar 2016-6-17
Hi,
I need to read the text file shown in the image below using a MATLAB script.I have tried the code below and I appreciate if someone can guide me to make it working. I have attached the text file here.
Thanks in advance.
myFolder = 'C:\Users\Desktop\'
filePattern = fullfile(myFolder, '*.txt');
csvFiles = dir(filePattern);
fmt='%d %4d/%2d/%2d %2d:%2d %d %*[^\n]';
for i=1:length(csvFiles)
fid = fopen(fullfile(myFolder,csvFiles(i).name));
c=cell2mat(textscan(fid,fmt,'headerlines',18,'collectoutput',1,'delimiter','\t'));
fid=fclose(fid);
end
  1 个评论
dpb
dpb 2016-6-14
Two problems, one easy, another "not so much"...
a) You can't mix types in 'collectoutput' and the floating point value fails with the %d format string so need to switch all %d to %f in the format string.
b) The file is NOT tab-delimited, it's the bane of C text input, blank-delimited with missing data. This is essentially impossible to deal with in C (and hence Matlab since it uses C formatted i/o routines derived from fscanf and friends). You can see the is make the above correction and return the intermediary result from textscan --
>> fmt='%f %4f/%2f/%2f %2f:%2f %f %*[^\n]';
>> d=cell2mat(textscan(fid,fmt,'headerlines',18,'collectoutput',1));
>> whos d
Name Size Bytes Class Attributes
d 1x7 56 double
>> d
d =
1.0e+04 *
2.3002 0.1997 0.0010 0.0001 0 0 0.0000
>> d(end)
ans =
0.2928
>>
This shows read the first record correctly; what happened that there's only one record???
>> frewind(fid) % we'll try again from the top...
Now read but find out where the file pointer is afterwards...
>> [d,n]=textscan(fid,fmt,1,'headerlines',18,'collectoutput',1);
>> n
n =
463865
>>
??? That's an awfully big number for one record, isn't it!!!???
C:\ML_R2012b\work> dir 023002_Q_1997.txt
Volume in drive C is unlabeled Serial number is BC9D:AAD0
Directory of c:\ml_r2012b\work\023002_q_1997.txt
023002_q_19► 463865 6/13/16 18:09
463,865 bytes in 1 file and 0 dirs 466,944 bytes allocate
113,018,556,416 bytes free
C:\ML_R2012b\work>
What we see is that's identically the file size; with no delimiter the skip-end-of-line went all the way to the end of the file.

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dpb
dpb 2016-6-15
编辑：dpb 2016-6-15
Well, since the file was malformed after all, here's how to clean it up and create a version which can then be read...
c=char(textread('023002_Q_1997.txt','%s','delimiter','\n','whitespace','','headerlines',18));
ix=[7 20:3:32 42];
c(:,ix)=',';
d=cell2mat(textscan(c(:,1:42).',repmat('%f',1,7),'collectoutput',1,'delimiter',','));
>> whos d
Name Size Bytes Class Attributes
d 8832x7 494592 double
>> d(1:10,:)
ans =
1.0e+04 *
2.3002 0.1997 0.0010 0.0001 0 0 0.0000
2.3002 0.1997 0.0010 0.0001 0 0.0015 NaN
2.3002 0.1997 0.0010 0.0001 0 0.0030 NaN
2.3002 0.1997 0.0010 0.0001 0 0.0045 NaN
2.3002 0.1997 0.0010 0.0001 0.0001 0 NaN
2.3002 0.1997 0.0010 0.0001 0.0001 0.0015 NaN
2.3002 0.1997 0.0010 0.0001 0.0001 0.0030 NaN
2.3002 0.1997 0.0010 0.0001 0.0001 0.0045 NaN
2.3002 0.1997 0.0010 0.0001 0.0002 0 NaN
2.3002 0.1997 0.0010 0.0001 0.0002 0.0015 NaN
>>
NB: Trotted out the old standby textread to read the file originally as a cellstring array as it does it without the need for the extra fopen/fclose pair and has all the flexibility needed for the purposes here.
The "magic numbers" were found by looking at the file in an editor and noting the columns following each numeric field, including the '/' and ':' for the date/time fields. These could have been done with string substitution or left as date/time fields but I just went ahead and turned the whole file into a csv file for simplicity.
Following that, saved the character array through the terminating comma after the last (possibly missing) numeric field and passed that to textscan. The key "trick" here is to remember storage is colum-major in Matlab so must transpose the array in memory to work by row from memory instead of down each column.
Also, there's a problem with the file format that the cast to char takes care of--on those records missing the final character the record length is short by a character and those that have a two-character trailing string are long by a character over the predominant length. This means don't actually have a fixed-length record file altho the first columns are fixed-width; another government contractor "feature", no doubt. :) This means can't just read the file as bytes and reshape but must scan for record terminators and then fixup.
Anyway, this should be something that works for all files.

更多回答（2 个）

dpb
dpb 2016-6-14
编辑：dpb 2016-6-15
Oh, one thing I noted also when checking on the delimiter; the EOL marker is '\r'; wonder what would happen if skip for it explicitly instead of the default '\n'?
>> fmt='%f %4f/%2f/%2f %2f:%2f %f %*[^\r]';
>> [d,n]=textscan(fid,fmt,'headerlines',18,'collectoutput',1,'endofline','\r')
d =
[2x7 double]
n =
1171
>>
OK, read the second record but croaked on missing value...what if create specific for it, too?
>> frewind(fid);
>> fmt1='%f %4f/%2f/%2f %2f:%2f %*[^\r]'; % format w/o the last float
>> [d,n]=textscan(fid,fmt1,11,'headerlines',18,'collectoutput',1,'endofline','\r')
d =
[11x6 double]
n =
4080
>>
Aha! Now we're getting somewhere; all we have to do is to wrap the two calls in a loop --
d=cell2mat(textscan(fid,fmt,1,'headerlines',18,'collectoutput',1,'endofline','\r')); % 1st record only
d=[d;[cell2mat(textscan(fid,fmt1,11,'collectoutput',1,'endofline','\r')) nan(11,1)]]; % next group
while ~feof(fid)
d=[d;[cell2mat(textscan(fid,fmt,1,'collectoutput',1,'endofline','\r'))];
d=[d;[cell2mat(textscan(fid,fmt1,11,'collectoutput',1,'endofline','\r')) nan(11,1)]];
end
While wouldn't normally dynamically allocate like this, unless the file is extremely large this should be "fast enough". It it does bog down excessively with time before finishing, preallocate a large array, keep index of rows read and store them appropriately.
  5 个评论
显示 3更早的评论
dpb
dpb 2016-6-15
编辑：dpb 2016-6-15
Well you can certainly count on the government to be there to "help"... :(
Only can eliminate a row by finding out which rows they are which is back to the line-by-line parsing.
All in all would likely be simpler to insert the delimiter; it's really quite simple to read a file as a 'blob' of characters.
Damith
Damith 2016-6-15
OK. Can you help me how to insert a delimiter and read the files?

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Shameer Parmar
Shameer Parmar 2016-6-17
For reading any text file.. try this code..
clear all;
count = 1;
fid = fopen('ascii_file.txt');
tline = fgetl(fid);
while ischar(tline)
if (tline ~= -1)
data(count,:) = {tline};
else
data(count,:) = {''};
end
count = count + 1;
tline = fgetl(fid);
end
fclose(fid);
replace 'ascii_file.txt' with your filename..
"data" will be the output (multi dimensional array), which store all your data from txt file.

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