cant extract surf features

i cant extract surf features from 120 folders when i use to detect surf features from the folders i shows and error undefiend function or variable here is my code..

function pushbutton3_Callback(hObject, eventdata, handles)
% hObject    handle to pushbutton3 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
% Start with a folder and get a list of all subfolders.
% Finds and prints names of all PNG, JPG, and TIF images in 
% that folder and all of its subfolders.
% Similar to imageSet() function in the Computer Vision System Toolbox: http://www.mathworks.com/help/vision/ref/imageset-class.html
clc;    % Clear the command window.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;

% Define a starting folder.
start_path = fullfile(matlabroot, '\toolbox\images\imdemos');
% Ask user to confirm or change.
topLevelFolder = uigetdir(start_path);
if topLevelFolder == 0
  return;
end
% Get list of all subfolders.
allSubFolders = genpath(topLevelFolder);
% Parse into a cell array.
remain = allSubFolders;
listOfFolderNames = {};
while true
  [singleSubFolder, remain] = strtok(remain, ';');
  if isempty(singleSubFolder)
    break;
  end
  listOfFolderNames = [listOfFolderNames singleSubFolder];
end
numberOfFolders = length(listOfFolderNames)

% Process all image files in those folders.
for k = 1 : numberOfFolders
  % Get this folder and print it out.
  thisFolder = listOfFolderNames{k};
  fprintf('Processing folder %s\n', thisFolder);
  
  % Get PNG files.
  filePattern = sprintf('%s/*.png', thisFolder);
  baseFileNames = dir(filePattern);
  % Add on TIF files.
  filePattern = sprintf('%s/*.tif', thisFolder);
  baseFileNames = [baseFileNames; dir(filePattern)];
  % Add on JPG files.
  filePattern = sprintf('%s/*.jpg', thisFolder);
  baseFileNames = [baseFileNames; dir(filePattern)];
  numberOfImageFiles = length(baseFileNames);
  % Now we have a list of all files in this folder.
  
  if numberOfImageFiles >= 1
    % Go through all those image files.
    for f = 1 : numberOfImageFiles
      fullFileName = fullfile(thisFolder, baseFileNames(f).name);
      fprintf('     Processing image file %s\n', fullFileName);
    end
  else
    fprintf('     Folder %s has no image files in it.\n', thisFolder);
  end
end

[Walter Roberson]

Please post a copy of the error message, everything in red.