MATLAB: Detecting Excel files without Excel extension

data parsingexceltext;xls

I need to be able to identify an Excel file without using xlsfinfo. It is a VERY slow function. Without it, my algorithm runs faster. Any ideas?

Background: Our test setup outputs text files that are named with the ".xls" extension. Back in Excel 2003 and before, if you named a tab delimited text file with "xls", Excel would open the file no problem and properly interpret it. Now, it is causing me headaches with importing data into MATLAB. MATLAB uses the ".xls" extension to check for wrong input to "textscan" and "importdata." Here is where it gets interesting. When you open a text file with the ".xls" extension and then save it, it is now an excel file and no longer tab delimited text file. Basically, I need to be able to tell the difference between text and Excel files without xlsfinfo because xlsfinfo is very slow.

Best Answer

You can try something like

fid = fopen(filename,'r');

fifty_bytes = fread(fid,50,'uint8'); fclose(fid);

Valid_characters = ['A':'Z' 'a':'z' ',./\ 0123456789' 9 10 13 '!"£$%^&*()[]{}-=_+ ... and any other valid characters you expect in your text files. ]

excel_file = false;

for i = 1:50

if any(fifty_bytes ~= Valid_characters)

excel_file = true;

end

Related Solutions

MATLAB: Problem opening excel csv file using xlsread

for CSV file you should use readtable() or csvread().

MATLAB: How Can I Write a Matrix to excel using ActXserver (or another way if needed!)

See my demo:

% Demo macro to write numerical arrays and cell arrays
% to two different worksheets in an Excel workbook file.
% Uses xlswrite1, available from the File Exchange
% http://www.mathworks.com/matlabcentral/fileexchange/10465-xlswrite1
function ExcelDemo
clc;
close all;
clear all;
fullFileName = GetXLFileName();
if isempty(fullFileName)
  % User clicked Cancel.

  return;
end
Excel = actxserver('Excel.Application');   
% Prepare proper filename extension.
% Get the Excel version because if it's version 11 (Excel 2003) the file extension should be .xls,
% but if it's 12.0 (Excel 2007) then we'll need to use an extension of .xlsx to avoid nag messages.
excelVersion = str2double(Excel.Version);
if excelVersion < 12
  excelExtension = '.xls';
else
  excelExtension = '.xlsx';
end
% Determine the proper format to save the files in.  It depends on the extension (Excel version).
switch excelExtension
  case '.xls' %xlExcel8 or xlWorkbookNormal
     xlFormat = -4143;
  case '.xlsb' %xlExcel12
     xlFormat = 50;
  case '.xlsx' %xlOpenXMLWorkbook
     xlFormat = 51;
  case '.xlsm' %xlOpenXMLWorkbookMacroEnabled 
     xlFormat = 52;
  otherwise
     xlFormat = -4143;
end
if ~exist(fullFileName, 'file')
  message = sprintf('I am going to create Excel workbook:\n\n%s\n\nClick OK to continue.\nClick Exit to exit this function', fullFileName);
  button = questdlg(message, 'Creating new workbook', 'OK', 'Exit', 'OK');
  drawnow;  % Refresh screen to get rid of dialog box remnants.
  if strcmpi(button, 'Exit')
    return;
  end
  % Add a new workbook.
  ExcelWorkbook = Excel.workbooks.Add;
  % Save this workbook we just created.
  ExcelWorkbook.SaveAs(fullFileName, xlFormat);
  ExcelWorkbook.Close(false);
else
  % Delete the existing file.
  delete(fullFileName);
end
% Open up the workbook named in the variable fullFileName.
invoke(Excel.Workbooks,'Open', fullFileName);
Excel.visible = true;
% Create some sample data.
myData = magic(20);
myOtherData = rand(10);
% Then run the new xlswrite1 function as many times as needed or in a loop 
% (for example xlswrite1(fullFileName, yourArrayName, XL_CellLocation). 
% IMPORTANT NOTE: the Excel object variable MUST exist in the routine that calls xlswrite1()
% and it MUST be named "Excel" EXACTLY because xlswrite1() has this line it it:
%   Excel = evalin('caller', 'Excel');
xlswrite1(fullFileName, myData, 'mySheetName', 'B2');
ca = {'Column Header 1', 'Column Header 2'};
xlswrite1(fullFileName, ca, 'mySheetName', 'B1');
ca = {'Row Header 1'; 'Row Header 2'};
xlswrite1(fullFileName, ca, 'mySheetName', 'A2');
xlswrite1(fullFileName, myOtherData, 'myOtherSheetName', 'B2');
% Delete all empty sheets in the active workbook.
DeleteEmptyExcelSheets(Excel);
% For fun, add comments to cells A1:A12 on sheet #1.
worksheets = Excel.sheets;
thisSheet = get(worksheets, 'Item', 1); 
for k = 1 : 12
  myComment = sprintf('Comment for cell A%d', k);
  cellReference = sprintf('A%d', k);
  theCell = thisSheet.Range(cellReference);
  theCell.AddComment(myComment);
end
% Then run the following code to close the activex server:
invoke(Excel.ActiveWorkbook,'Save');
Excel.Quit;
Excel.delete;
clear Excel;
message = sprintf('Done!\nThis Excel workbook has been created:\n%s', fullFileName);
msgbox(message);
% End of main function: ExcelDemo.m -----------------------------
%--------------------------------------------------------------------
% Gets the name of the workbook from the user.
function fullExcelFileName = GetXLFileName()
  fullExcelFileName = [];  % Default.
  % Ask user for a filename.
  FilterSpec = {'*.xls', 'Excel workbooks (*.xls)'; '*.*', 'All Files (*.*)'};
  DialogTitle = 'Save workbook file name';
  % Get the default filename.  Make sure it's in the folder where this m-file lives.
  % (If they run this file but the cd is another folder then pwd will show that folder, not this one.
  thisFile = mfilename('fullpath');
  [thisFolder, baseFileName, ext] = fileparts(thisFile);
  DefaultName = sprintf('%s/%s.xls', thisFolder, baseFileName);
  [fileName, specifiedFolder] = uiputfile(FilterSpec, DialogTitle, DefaultName);
  if fileName == 0
    % User clicked Cancel.
    return;
  end
  % Parse what they actually specified.
  [folder, baseFileName, ext] = fileparts(fileName);
  % Create the full filename, making sure it has a xls filename.
  fullExcelFileName = fullfile(specifiedFolder, [baseFileName '.xls']);
% --------------------------------------------------------------------
% DeleteEmptyExcelSheets: deletes all empty sheets in the active workbook.
% This function looped through all sheets and deletes those sheets that are
% empty. Can be used to clean a newly created xls-file after all results
% have been saved in it.
function DeleteEmptyExcelSheets(excelObject)
%   excelObject = actxserver('Excel.Application');
%   excelWorkbook = excelObject.workbooks.Open(fileName);
  worksheets = excelObject.sheets;
  sheetIdx = 1;
  sheetIdx2 = 1;
  numSheets = worksheets.Count;
  % Prevent beeps from sounding if we try to delete a non-empty worksheet.
  excelObject.EnableSound = false;
  % Loop over all sheets
  while sheetIdx2 <= numSheets
    % Saves the current number of sheets in the workbook
    temp = worksheets.count;
    % Check whether the current worksheet is the last one. As there always
    % need to be at least one worksheet in an xls-file the last sheet must
    % not be deleted.
    if or(sheetIdx>1,numSheets-sheetIdx2>0)
      % worksheets.Item(sheetIdx).UsedRange.Count is the number of used cells.
      % This will be 1 for an empty sheet.  It may also be one for certain other
      % cases but in those cases, it will beep and not actually delete the sheet.
      if worksheets.Item(sheetIdx).UsedRange.Count == 1
        worksheets.Item(sheetIdx).Delete;
      end
    end
    % Check whether the number of sheets has changed. If this is not the
    % case the counter "sheetIdx" is increased by one.
    if temp == worksheets.count;
      sheetIdx = sheetIdx + 1;
    end
    sheetIdx2 = sheetIdx2 + 1; % prevent endless loop...
  end
  excelObject.EnableSound = true;
  return;

Best Answer

Related Solutions

MATLAB: Problem opening excel csv file using xlsread

MATLAB: How Can I Write a Matrix to excel using ActXserver (or another way if needed!)

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