MATLAB: Select rows from txt file

MATLABselect rows from txt filestringstext file

Hi,
Could someone help on how can I choose specific rows from the below sample (the original txt file is actually huge):
Stock Date Time Price Volume Stock Category > ETE 04/01/2010 10145959 18.34 500 Big Cap > ETE 04/01/2010 10150000 18.34 70 Big Cap > ETE 04/01/2010 10170000 18.34 430 Big Cap > ABC 04/01/2010 10190000 18.34 200 Big Cap > YYY 04/01/2010 10200000 18.34 100 Big Cap > ETE 04/01/2010 10250000 18.34 40 Big Cap > ETE 04/01/2010 10295959 18.34 215 Big Cap > ETE 04/01/2010 10300000 18.34 500 Big Cap > ETE 04/01/2010 10320000 18.34 500 Big Cap
For instance can I keep only rows for stock 'ABC' (column 1)?
Thanks in advance,
Panos

Best Answer

How are you going to store the data once you get it? Do you just want the text? Or do you actually want to read in data? If the latter, you'll need to store the data in some kind of flexible container, like a cell array. Unfortunately, this will increase your memory requirements (which could be a problem, given that you said the file is huge). Here are some options you could try. Try them on the small example to see the various formats for the result. In particular, keep an eye on the bytes used, if memory is an issue.
Option 1:
fid = fopen('stocks.txt');
data = textscan(fid,'%s%s%f%f%f%[^\n]','delimiter',' ','headerlines',1);
idx = strcmp('ETE',data{1});
f = @(x) x(idx);
ETEdata = cellfun(f,data,'uniformoutput',false)
whos ETEdata
fclose(fid);
Option 2:
fid = fopen('stocks.txt');
hdr = textscan(fid,'%s%s%s%s%s%[^\n]',1,'delimiter',' ');
ETEdata = {};
while ~feof(fid)
    thisdata = textscan(fid,'%s%s%f%f%f%[^\n]',1,'delimiter',' ');
    if strcmp(thisdata{1},'ETE')
        ETEdata = [ETEdata;{thisdata{1}{1},thisdata{2}{1},...
            thisdata{3:5},thisdata{6}{1}}];
    end
end
fclose(fid);
ETEdata
whos ETEdata
Option 3 (requires Statistics Toolbox):
fid = fopen('stocks.txt');
hdr = textscan(fid,'%s%s%s%s%s%[^\n]',1,'delimiter',' ');
fclose(fid);
hdr = [hdr{:}];
hdr = regexprep(hdr,'\W','');
data = dataset('file','stocks.txt','format','%s%s%f%f%f%[^\n]',...
    'delimiter',' ','headerlines',1,'readvarnames',false);
data.Properties.VarNames = hdr
data.Stock = nominal(data.Stock);
data.StockCategory = nominal(data.StockCategory);
ETEdata = data(data.Stock == 'ETE',:)
whos ETEdata
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