Reading a text file containing strings and numeric data

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ZHU QIXUAN
ZHU QIXUAN 2021-3-1
评论： ZHU QIXUAN 2021-3-1
Hi,
I have a .dat file like this:
Time 0.000000400
154 -1 1.77472 1.34813 0.14000 -0.00418 -0.00188 0.00042
155 -1 0.32897 1.41804 0.14000 0.00034 -0.00181 -0.00068
Time 0.000000500
389 -1 1.28893 1.39899 0.12000 0.00304 -0.00191 -0.00033
Time 0.000000600
512 -1 1.86454 1.13224 0.12000 0.00433 -0.00175 -0.00084
520 -1 0.21448 1.44465 0.12000 -0.00033 -0.00190 0.00037
Time 0.000000800
677 -1 1.14717 1.54507 0.12000 -0.00272 -0.00194 0.00005
692 -1 0.64696 1.33344 0.12000 -0.00145 -0.00188 0.00048
697 -1 0.46609 1.33894 0.12000 -0.00097 -0.00187 0.00050
I only need store the numbers and the digital time into two seperate array.
The number of rows of data at each time is not the same, but the number of columns is the same.
Final arrays should look like this:
For numerical data:
154 -1 1.77472 1.34813 0.14000 -0.00418 -0.00188 0.00042
155 -1 0.32897 1.41804 0.14000 0.00034 -0.00181 -0.00068
389 -1 1.28893 1.39899 0.12000 0.00304 -0.00191 -0.00033
512 -1 1.86454 1.13224 0.12000 0.00433 -0.00175 -0.00084
520 -1 0.21448 1.44465 0.12000 -0.00033 -0.00190 0.00037
677 -1 1.14717 1.54507 0.12000 -0.00272 -0.00194 0.00005
692 -1 0.64696 1.33344 0.12000 -0.00145 -0.00188 0.00048
697 -1 0.46609 1.33894 0.12000 -0.00097 -0.00187 0.00050
For digital time:
0.000000400
0.000000500
0.000000600
0.000000800
Total data exceeds 5 million rows, I tried to use xlsread function, but this function is limited to around 1 million rows.
Any help would be appreciated.

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采纳的回答

Jan
Jan 2021-3-1
编辑：Jan 2021-3-1
fid = fopen(File, 'r');
if fid < 0, error('Cannot open file'); end
TimeLen = 1e6;
TimeIndex = 0;
Time = zeros(1, TimeLen);
DataLen = 5e6
DataIndex = 0;
Data = zeros(8, DataLen);
while 1
C = fgetl(fid);
if ~ischar(C) % or: feof(fid)
break;
end
if strncmpi(C, 'Time', 4)
TimeIndex = TimeIndex + 1;
if TimeIndex > TimeLen
TimeLen = TimeLen + 1000;
Time(TimeLen) = 0; % Append zeros
end
Time(TimeIndex) = sscanf(C, 'Time %g', 1);
else
DataIndex = DataIndex + 1;
if DataIndex > DataLen
DataLen = DataLen + 10000;
Data(:, DataLen) = 0; % Append zeros
end
Data(:, DataIndex) = sscanf(C, '%g', [8, 1]);
end
end
fclose(fid);
Time = Time(1:TimeIndex); % Crop unused memory
Data = Data(:, 1:DataIndex);
An alternativ is reading the text at once:
S = fileread(FileName);
C = strsplit(S, '\n');
isTime = strncmp(C, 'Time', 4);
STime = sprintf('%s ', C{isTime});
Time = sscanf(STime, 'Time %g ', [1, inf]);
C(isTime) = [];
SData = sprintf('%s ', C{:});
Data = sscanf(SData, '%g', [8, inf]).';
This will take more RAM, but I assume it is faster.
By the way: Text files are useful, if the are read or edited by human. In your case a binary file with a simple structure would have been more efficient.
  1 个评论
ZHU QIXUAN
ZHU QIXUAN 2021-3-1
Hi Jan,
That really helps a lot! I like your second method, which can be finished in 30s. Thank you so much.

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