如何在Matlab中打开DBase文件(.DBF)? [英] How to open DBase files (.DBF) in Matlab?
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问题描述
我已经在Matlab Central上进行了搜索和搜索，但是找不到任何直接在Matlab中打开DBF文件的方法.在TMW File Exchange中有一些对DBFREAD函数的引用，但现在不再可用.真的有问题吗?
I've googled and searched through Matlab Central, but cannot find any way to open DBF files directly in Matlab. There are some references to DBFREAD function in TMW File Exchange, but it's not available anymore. Is it really a problem?
我确实有数据库工具箱，但是在那里找不到dbf支持.
I do have Database toolbox, but could not find dbf support there.
我不想使用Excel或其他工具在Matlab之外转换文件，因为我有很多文件要处理. ODBC也不是很好，我也需要代码在Mac和Unix下工作.
I don't want to use Excel or other tools for converting files outside of Matlab, since I have a lot of files to process. ODBC also is not good, I need the code to work under Mac and Unix as well.
请帮助.
推荐答案
我联系了DBFREAD函数的作者Brian Madsen，该函数已从File Exchange中删除，原因可能是MathWorks打算在某些情况下将其包含在MATLAB中将来的版本. Brian允许我在这里发布此功能.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.
I contacted with Brian Madsen, the author of DBFREAD function, which was deleted from File Exchange, probably because The Mathworks is going to include this function into MATLAB in some future release. Brian kindly gave me permission to publish this function here. All copyright information left intact. I only modified lines 33-38 to allow DBFREAD to read file outside working directory.
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
STR2DOUBLE2CELL子功能有时会无法正常工作(请参见此讨论).
STR2DOUBLE2CELL subfunction sometimes works incorrectly if number of digits in the input parameter is different (see this discussion).
这是我的STR2DOUBLE2CELL版本:
Here is my version of 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);
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