如何在 Matlab 中打开 DBase 文件（.DBF）？

Question

我已经通过 Google 搜索并通过 Matlab Central 进行搜索，但找不到任何直接在 Matlab 中打开 DBF 文件的方法。 TMW File Exchange 中有一些对 DBFREAD 函数的引用，但它不再可用。真的有问题吗？

我确实有数据库工具箱，但在那里找不到 dbf 支持。

我不想使用 Excel 或其他工具在 Matlab 之外转换文件，因为我有很多文件需要处理。 ODBC 也不好，我需要代码也能在 Mac 和 Unix 下工作。

请帮忙。

Answer 1

我联系了 DBFREAD 函数的作者 Brian Madsen，该函数已从 File Exchange 中删除，可能是因为 Mathworks 将在未来的某个版本中将此函数包含到 MATLAB 中。 Brian 好心允许我在这里发布这个函数。所有版权信息均保持不变。我只修改了第 33-38 行以允许 DBFREAD 读取工作目录之外的文件。

function [dbfData, dbfFieldNames] = dbfread(filename, records2read, requestedFieldNames)
%DBFREAD Read the specified records and fields from a DBF file.
%
%   [DATA, NAMES] = DBFREAD(FILE) reads numeric, float, character and date
%   data and field names from a DBF file, FILE.
%
%   [DATA, NAMES] = DBFREAD(FILE, RECORDS2READ) reads only the record
%   numbers specified in RECORDS2READ, a scalar or vector.
%
%   [DATA, NAMES] = DBFREAD(FILE, RECORDS2READ, REQUESTEDFIELDNAMES) reads
%   the data from the fields, REQUESTEDFIELDNAMES, for the specified
%   records. REQUESTEDFIELDNAMES must be a cell array. The fields in the
%   output will follow the order given in REQUESTEDFIELDNAMES.
%
%   Examples:
%
%       % Get all records and a list of the field names from a DBF file.
%       [DATA,NAMES] = dbfread('c:\matlab\work\mydbf')
%
%       % Get data from records 3:5 and 10 from a DBF file.
%       DATA = dbfread('c:\matlab\work\mydbf',[3:5,10])
%
%       % Get data from records 1:10 for three of the fields in a DBF file.
%       DATA = dbfread('c:\matlab\work\mydbf',1:10,{'FIELD1' 'FIELD3' 'FIELD5'})
%
%   See also XLSREAD, DLMREAD, DLMWRITE, LOAD, FILEFORMATS, TEXTSCAN.

% Copyright 2008 The MathWorks, Inc.
% $Revision: 1.0 $   $Date: 2008/04/18 05:58:17 $

[pathstr,name,ext] = fileparts(filename);

dbfFileId = fopen(filename,'r','ieee-le');
if (dbfFileId == -1)
    dbfFileId = fopen(fullfile(pathstr, [name '.dbf']),'r','ieee-le');
end
if (dbfFileId == -1)
    dbfFileId = fopen(fullfile(pathstr, [name '.DBF']),'r','ieee-le');
end

if (dbfFileId == -1)
    eid = sprintf('MATLAB:%s:missingDBF', mfilename);
    msg = sprintf('Failed to open file %s.dbf or file %s.DBF.',...
            name, name);
    error(eid,'%s',msg)
end

info = dbfinfo(dbfFileId);
if ~exist('requestedFieldNames','var')
    dbfFieldNames = {info.FieldInfo.Name};
    requestedFieldNames = dbfFieldNames;
else
    dbfFieldNames = (info.FieldInfo(matchFieldNames(info,requestedFieldNames)).Name);
end
fields2read = matchFieldNames(info,requestedFieldNames);

% The first byte in each record is a deletion indicator
lengthOfDeletionIndicator = 1;

if ~exist('records2read','var')
    records2read = (1:info.NumRecords);
elseif max(records2read) > info.NumRecords
    eid = sprintf('MATLAB:%s:invalidRecordNumber', mfilename);
    msg = sprintf('Record number %d does not exist, please select from the range 1:%d.',...
        max(records2read), info.NumRecords);
    error(eid,'%s',msg)
end

% Loop over the requested fields, reading in the data
dbfData = cell(numel(records2read),numel(fields2read));
for k = 1:numel(fields2read),
    n = fields2read(k);
    fieldOffset = info.HeaderLength ...
                  + sum([info.FieldInfo(1:(n-1)).Length]) ...
                  + lengthOfDeletionIndicator;
    fseek(dbfFileId,fieldOffset,'bof');
    formatString = sprintf('%d*uint8=>char',info.FieldInfo(n).Length);
    skip = info.RecordLength - info.FieldInfo(n).Length;
    data = fread(dbfFileId,[info.FieldInfo(n).Length info.NumRecords],formatString,skip);
    dbfData(:,k) = feval(info.FieldInfo(n).ConvFunc,(data(:,records2read)'));
%     dbfData(:,k) = info.FieldInfo(n).ConvFunc(data(:,records2read)');
end

fclose(dbfFileId);

%--------------------------------------------------------------------------
function fields2read = matchFieldNames(info, requestedFieldNames)
% Determine which fields to read.

allFieldNames = {info.FieldInfo.Name};
if isempty(requestedFieldNames)
    if ~iscell(requestedFieldNames)
        % Default case: User omitted the parameter, return all fields.
        fields2read = 1:info.NumFields;
    else
        % User supplied '{}', skip all fields.
        fields2read = [];
    end
else
    % Match up field names to see which to return.
    fields2read = [];
    for k = 1:numel(requestedFieldNames)
        index = strmatch(requestedFieldNames{k},allFieldNames,'exact');
        if isempty(index)
            wid = sprintf('MATLAB:%s:nonexistentDBFName',mfilename);
            wrn = sprintf('DBF name ''%s'' %s\n%s',requestedFieldNames{k},...
                     'doesn''t match an existing DBF name.',...
                     '         It will be ignored.');
            warning(wid,wrn)
        end
        for l = 1:numel(index)
            % Take them all in case of duplicate names.
            fields2read(end+1) = index(l);
        end
    end
end

%--------------------------------------------------------------------------

function info = dbfinfo(fid)
%DBFINFO Read header information from DBF file.
%   FID File identifier for an open DBF file.
%   INFO is a structure with the following fields:
%      Filename       Char array containing the name of the file that was read
%      DBFVersion     Number specifying the file format version
%      FileModDate    A string containing the modification date of the file
%      NumRecords     A number specifying the number of records in the table
%      NumFields      A number specifying the number of fields in the table
%      FieldInfo      A 1-by-numFields structure array with fields:
%         Name        A string containing the field name 
%         Type        A string containing the field type 
%         ConvFunc    A function handle to convert from DBF to MATLAB type
%         Length      A number of bytes in the field
%      HeaderLength   A number specifying length of the file header in bytes
%      RecordLength   A number specifying length of each record in bytes

%   Copyright 1996-2005 The MathWorks, Inc.
%   $Revision: 1.1.10.4 $  $Date: 2005/11/15 01:07:13 $

[version, date, numRecords, headerLength, recordLength] = readFileInfo(fid);
fieldInfo = getFieldInfo(fid);

info.Filename     = fopen(fid);
info.DBFVersion   = version;
info.FileModDate  = date;
info.NumRecords   = numRecords;
info.NumFields    = length(fieldInfo);
info.FieldInfo    = fieldInfo;
info.HeaderLength = headerLength;
info.RecordLength = recordLength;

%----------------------------------------------------------------------------
function [version, date, numRecords, headerLength, recordLength] = readFileInfo(fid)
% Read from File Header.

fseek(fid,0,'bof');

version = fread(fid,1,'uint8');

year  = fread(fid,1,'uint8') + 1900;
month = fread(fid,1,'uint8');
day   = fread(fid,1,'uint8');

dateVector = datevec(sprintf('%d/%d/%d',month,day,year));
dateForm = 1;% dd-mmm-yyyy
date = datestr(dateVector,dateForm);

numRecords   = fread(fid,1,'uint32');
headerLength = fread(fid,1,'uint16');
recordLength = fread(fid,1,'uint16');

%----------------------------------------------------------------------------
function fieldInfo = getFieldInfo(fid)
% Form FieldInfo by reading Field Descriptor Array.
%
% FieldInfo is a 1-by-numFields structure array with the following fields:
%       Name      A string containing the field name 
%       Type      A string containing the field type 
%       ConvFunc  A function handle to convert from DBF to MATLAB type
%       Length    A number equal to the length of the field in bytes

lengthOfLeadingBlock    = 32;
lengthOfDescriptorBlock = 32;
lengthOfTerminator      =  1;
fieldNameOffset         = 16;  % Within table field descriptor
fieldNameLength         = 11;

% Get number of fields.
fseek(fid,8,'bof');
headerLength = fread(fid,1,'uint16');
numFields = (headerLength - lengthOfLeadingBlock - lengthOfTerminator)...
               / lengthOfDescriptorBlock;

% Read field lengths.
fseek(fid,lengthOfLeadingBlock + fieldNameOffset,'bof');
lengths = fread(fid,[1 numFields],'uint8',lengthOfDescriptorBlock - 1);

% Read the field names.
fseek(fid,lengthOfLeadingBlock,'bof');
data = fread(fid,[fieldNameLength numFields],...
             sprintf('%d*uint8=>char',fieldNameLength),...
             lengthOfDescriptorBlock - fieldNameLength);
data(data == 0) = ' '; % Replace nulls with blanks
names = cellstr(data')';

% Read field types.
fseek(fid,lengthOfLeadingBlock + fieldNameLength,'bof');
dbftypes = fread(fid,[numFields 1],'uint8=>char',lengthOfDescriptorBlock - 1);

% Convert DBF field types to MATLAB types.
typeConv = dbftype2matlab(upper(dbftypes));

% Return a struct array.
fieldInfo = cell2struct(...
    [names;  {typeConv.MATLABType}; {typeConv.ConvFunc}; num2cell(lengths)],...
    {'Name', 'Type',                'ConvFunc',          'Length'},1)';

%----------------------------------------------------------------------------
function typeConv = dbftype2matlab(dbftypes)
% Construct struct array with MATLAB types & conversion function handles.

typeLUT = ...
    {'N', 'double', @str2double2cell;...   % DBF numeric
     'F', 'double', @str2double2cell;...   % DBF float
     'C', 'char',   @cellstr;...           % DBF character
     'D', 'char',   @cellstr};             % DBF date

unsupported = struct('MATLABType', 'unsupported', ...
                     'ConvFunc',   @cellstr);

% Unsupported types: Logical,Memo,N/ANameVariable,Binary,General,Picture

numFields = length(dbftypes);
if numFields ~= 0
  typeConv(numFields) = struct('MATLABType',[],'ConvFunc',[]);
end
for k = 1:numFields
    idx = strmatch(dbftypes(k),typeLUT(:,1));
    if ~isempty(idx)
        typeConv(k).MATLABType = typeLUT{idx,2};
        typeConv(k).ConvFunc   = typeLUT{idx,3};
    else
        typeConv(k) = unsupported;
    end
end

%----------------------------------------------------------------------------
function out = str2double2cell(in)
% Translate IN, an M-by-N array of class char, to an M-by-1 column vector
% OUT, of class double.  IN may be blank- or null-padded. If IN(k,:) does
% not represent a valid scalar value, then OUT(k) has value NaN.
if isempty(in)
    out = {[NaN]};
    return
end

% Use sprintf when possible, but fall back to str2double for unusual cases.
fmt = sprintf('%%%df',size(in,2));
[data count] = sscanf(reshape(in',[1 numel(in)]),fmt);
if count == size(in,1)
    out = cell(count,1);
    for k = 1:count
        out{k} = data(k);
    end
else
    out = num2cell(str2double(cellstr(in)));
end

---

更新

如果输入参数中的位数不同，STR2DOUBLE2CELL 子函数有时无法正常工作（请参阅 此讨论）。

这是我的 STR2DOUBLE2CELL 版本：

function out = str2double2cell(in)
% Translate IN, an M-by-N array of class char, to an M-by-1 column vector
% OUT, of class double.  IN may be blank- or null-padded. If IN(k,:) does
% not represent a valid scalar value, then OUT(k) has value NaN.
if isempty(in)
    out = {[NaN]};
    return
end

out = cellfun(@str2double,cellstr(in),'UniformOutput',false);

Answer 2

在我看来，你有两个选择：

方法 1：使用 ODBC 读取 dBASE 文件：

这需要数据库工具箱

cd 'path/to/dbf/files/'
conn = database('dBASE Files', '', '');
cur = exec(conn, 'select * from table');
res = fetch(cur);
res.Data
close(conn)

'dBASE Files' 是 ODBC 数据源名称 (DSN)（我相信默认情况下随 MS Office 安装）。它使用当前目录来查找 .dbf 文件。

或者，您可以使用无 DSN 的连接字符串，例如：

driver = 'sun.jdbc.odbc.JdbcOdbcDriver';
url = 'jdbc:odbc:DRIVER={Microsoft dBase Driver (*.dbf)};DBQ=x:\path;DefaultDir=x:\path';
conn = database('DB', '', '', driver, url);
...

如果这给您带来麻烦，请尝试使用 FoxPro ODBC 驱动程序。

对于 Linux/Unix，可以执行相同的操作。快速搜索发现了这些：

• How do set up an ODBC DSN on Mac or Linux/Unix
• 如何通过 OpenOffice 创建和使用 dBase 格式文件

方法 2 ：直接使用库读取/写入 .dbf 文件

SVConsulting 提供了一个免费的 Java 库，它允许您读取/写入 DBF 文件：JDBF。 （更新：链接似乎已失效，请使用Wayback Machine 来访问它）

您可以直接从 MATLAB 使用 Java 类。请参阅文档了解具体操作方法。

Answer 3

如果您只对数值感兴趣，请尝试 xlsread 命令。