problem in strcat

Question

Pap 2011-4-17

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/5686-problem-in-strcat

采纳的回答： Walter Roberson

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Hello,

%I use the below sample of huge txt file:

ETE 04/01/2010 10145959 18.31 500 Big Cap

ETE 04/01/2010 10150000 18.01 70 Big Cap

ETE 04/01/2010 10170000 18.54 430 Big Cap

ABC 04/01/2010 10190000 18.34 200 Big Cap

%Then, I use the below codes to create a new binary column 'TRADE' with values 'Buy' or 'Sale'.

% Read stock data from file fid = fopen('stocks.txt');

data = textscan(fid,'%s%s%f%f%f%[^\n]','delimiter',' ','headerlines',1);

% Read as text (for later writing)

 frewind(fid);
  txt = textscan(fid,'%s','delimiter','\n');
  fclose(fid);

% Get prices from imported data

Price = data{4};

% Determine which stocks to buy

buy = [true;diff(Price)>=0];
idx = find(~diff(Price));
buy(idx+1) = buy(idx);

% Make string of trade decision

buysell = cellstr(repmat(' Sell',size(Price)));
buysell(buy) = {' Buy'};

% Open file for writing fid = fopen('stocks2.txt','wt');

% Make output string by appending trade decision outstr = strcat(txt{1},[' Trade';buysell]);

% Write out fprintf(fid,'%s\n',outstr{:}); fclose(fid);

% When I apply these codes to the sample file (53 MB) it works fine, but when I apply this to the original file (540 MB) there is the below error message:

outstr = strcat(txt{1},[' Trade';buysell]);
??? Error using ==> cell.strcat at 50
All the inputs must be the same size or scalars.

Could anyone help on what the above pertains to, and how can I solve this problem?

Many thanks in advance,

Panos

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Answer 1

Walter Roberson 2011-4-17

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https://ww2.mathworks.cn/matlabcentral/answers/5686-problem-in-strcat#answer_7929

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I have edited your tags and title because your problem had nothing to do with "outstr", which is merely the name of the variable you happened to be assigning the result to.

You need to refer to the strcat documentation

Inputs can be combinations of single strings, strings in scalar cells, character arrays with the same number of rows, and same-sized cell arrays of strings.

So your problem is that txt{1} does not have the same number of rows as the [' Trade';buysell] expression does. This is because you are adding a header line for that portion, but you do not add a corresponding header (even an empty string) to the first part.