Question

我有一个包含所有数字数据的文本文件，每行代码如下所示

标签index1：value1 index2：value2。。。 index8：value8

示例行：

1 1:0.731641 2:0.0445045 3:0.959925 4:1 6:0.366283 7:0.304412 8:0.616054

任何索引上的行都可能缺少值，如何使用此文件形成9列的矩阵？

Answer 1

您可以使用textscan和%d:%f格式说明符来获取此信息。这是一个完整的例子，说明如何做到这一点。

fid = fopen(filename, 'r');

%// Get the label of the first line
label = fscanf(fid, '%d', 1);

%// Initialize matrix to hold the result
%// If you know what the maximum label will be you can make this the right size
m = zeros(0,9);

%// Row counter
row = 1;

%// Loop until we hit the end of the file
while ~feof(fid)
    %// Look for a number followed by a colon and another number
    data = textscan(fid, '%d:%f');

    values = data{2};
    columns = data{1}(1:numel(values));

    %// Fill the matrix at the columns that we loaded using the label as the row
    m(row, columns) = values;

    %// The next label was automatically picked up because it matched %d

    row = row + 1;
end

fclose(fid);

我在以下输入上对此进行了测试：

1 1:0.73  2:0.04  3:0.95  4:1  6:0.36  7:0.30  8:0.61
2 2:0.99  2:0.45  5:0.99  4:2  7:0.5  9:10
3 1:-2  9:12

并且能够生成以下矩阵

m =
    0.73   0.04   0.95     1      0   0.36   0.3   0.61    0
       0   0.45      0     2   0.99      0   0.5      0   10
      -2      0      0     0      0      0     0      0   12

<强>更新

如果你有一个非常大的矩阵并且它是稀疏填充的，你可以使用类似下面的东西从数据中创建一个稀疏矩阵。

fid = fopen(filename, 'r');

%// Get the label of the first line
label = fscanf(fid, '%d', 1);

%// Initialize rows/cols/values array
[rows, cols, vals] = deal([]);

%// Row counter
row = 1;

%// Loop until we hit the end of the file
while ~feof(fid)
    %// Look for a number followed by a colon and another number
    data = textscan(fid, '%d:%f');
    columns = data{1}(1:numel(data{2}));

    %// Append data to rows/cols/vals arrays
    vals = cat(1, vals(:), data{2});
    cols = cat(1, cols(:), double(columns(:)));
    rows = cat(1, rows(:), row + zeros(size(columns(:))));

    %// The next label was automatically picked up because it matched %d

    row = row + 1;  
end

fclose(fid);

%// Create the sparse matrix
m = sparse(rows, cols, vals);

从文本文件matlab形成矩阵

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