Matlab xlsread 在行 1048576 后切断文件 [英] Matlab xlsread cutting off file after row 1048576

问题描述

除了 xlsread(file.csv) 之外，还有没有其他方法可以将 Excel 格式的 .csv 导入到 Matlab 中；

Is there any other way of importing an Excel formatted .csv into Matlab other than xlsread(file.csv);

我拥有的文件包含 2830082 行，而 xlsread 读取时似乎有 1048576 行的限制 - 其余部分被切断.

The file I have contains 2830082 lines, and xlsread seems to have a limit of 1048576 lines when reading it - the rest gets cut off.

文件看起来像:

Time, Value
12:07:29, -1.13
12:07:29, -7.54
...

因此，由于日期格式的原因，使用 csvread(..) 是行不通的.

So using csvread(..) isn't going to work because of the date format.

推荐答案

我发现将大 csv 文件读入 Matlab 的最快方法是对它们进行内存映射并将内容解析为单个字符串.尝试使用此示例代码:

I've found the fastest way to read BIG csv files into Matlab is to memory-map them and parse the contents as a single string. Try playing with this example code:

fname = 'file.csv';
fstats = dir(fname);
% Map the file as one long character string
m = memmapfile(fname, 'Format', {'uint8' [ 1 fstats.bytes] 'asUint8'});
textdata = char(m.Data(1).asUint8);

% Find the end of each line, and use the line ends to form an index array
row = strfind(textdata, sprintf('
'));
row = [[1; row(1:end-1)'+2] row' - 1];
% Fix-up if there is no 
 at the end of the last line
if (row(end) < fstats.bytes - 2)
    row = [row; [row(end) + 2, fstats.bytes]];
end
numrows = size(row, 1);
% Create output variables
Time = zeros(numrows, 1);
Value = zeros(numrows, 1);

% Parse each line of the data (I'm ignoring the first line for simplicity)
for RowNum = 2:numrows
    data = textscan(textdata(row(RowNum,1):row(RowNum,2)), '%[^,]%f', 'delimiter', ',');
    Time(RowNum) = datenum(data{:});
    Value(RowNum) = data{2};
end

% Remove the file mapping
clear('m');

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