如何在Matlab中打开DBase文件(.DBF)?

7
我已经谷歌和在Matlab Central上搜索过了,但是找不到任何直接在Matlab中打开DBF文件的方法。 有一些关于TMW文件交换中的DBFREAD函数的参考资料,但现在已经不可用了。这真的是一个问题吗?
我确实拥有数据库工具箱,但是在那里找不到dbf支持。
我不想使用Excel或其他工具在Matlab之外转换文件,因为我有很多要处理的文件。 ODBC也不好用,我需要代码在Mac和Unix下运行。
请帮忙。
3个回答

11

我联系了DBFREAD函数的作者Brian Madsen,该函数被从文件交换中删除,可能是因为The Mathworks将在未来的某个版本中将此函数包含到MATLAB中。 Brian很慷慨地允许我在这里发布这个函数。版权信息保持不变。 我只修改了33-38行,以允许DBFREAD读取工作目录外的文件。

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

如果输入参数中数字的位数不同,STR2DOUBLE2CELL子函数有时会工作不正确(请参见此讨论)。

这是我的版本STR2DOUBLE2CELL:

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);

刚刚发现这个。仍然运行得很好。在我的当前版本的Matlab(8.0.0.783(R2012b))中,dbf文件无法读取。 - Josh Vander Hook
@yuk 刚刚尝试了这个函数,不幸的是它对我不起作用。这可能是因为我的数据问题还是因为这个函数已经过时了? - Max
@Max:我已经有一段时间没有使用它了,所以我不确定它是否适用于新的MATLAB版本。出了什么问题?你可能需要提出一个新的问题或联系Brian Madsen。我听说他现在在Mathworks工作。 - yuk

6
我认为,您有两个选择:

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' 是一个ODBC数据源名称(DSN)(我相信它是默认与MS Office一起安装的)。它使用当前目录查找.dbf文件。

或者你可以使用类似以下内容的无DSN连接字符串:

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

如果出现问题,请尝试使用FoxPro ODBC驱动程序。

对于Linux/Unix,也可以做同样的事情。快速搜索发现以下内容:

方法2:使用库直接读写.dbf文件

有一个Java库可供免费使用,可以读写DBF文件:SVConsulting提供的JDBF。(更新:链接似乎已失效,请使用Wayback Machine进行访问)

您可以直接从MATLAB中使用Java类。请参阅文档以了解详细信息。


JDBC和Matlab类是可行的方法。在几个Matlab类后面隐藏平台特定的和Java代码,您就可以开始工作了。我有很多生产代码是依赖于数据库的,并且它是轻松多平台的(在Win上进行Dev/Test,在Linux上进行Test/Run)。只需简单地将代码移到其他平台上,运行即可,没有问题。我们尝试了ODBC,使用了众所周知的数据库(Oracle、PostgreSQL),但需要进行无休止的调试 - ODBC实现略有不同。 - Marc
您不需要使用数据库工具箱来执行方法1。使用数据库工具箱可能会更加方便,但是您可以在没有数据库工具箱的情况下建立JDBC连接。 - Adrian
谢谢您的回答。我一定会尝试使用Java库来实现这个函数。只是很奇怪为什么还没有人做过这样的事情。 - yuk
@Marc:你说得对,我只是碰巧找不到免费的dBase JDBC驱动程序,也许你可以帮忙解决一下.. @Adrian:我使用工具箱是因为OP已经提到了它。 - Amro
@Amro:抱歉,这是新手问题:OP代表什么?SO俚语? :) - yuk

0
如果您只对数字值感兴趣,请尝试使用xlsread命令。

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