Question

I have a multispectral image and I’ve a question. I’ve found a function code on the internet which allows to read this kind of images. The problem is I received the following error:

??? function [lan_data] = lanread('montana.lan')
    |
Error: Function definitions are not
permitted in this context.

Also, when I checked the help of the ‘lanread’ command I received the following information: “>> help landread

landread not found.”

Is possible that this command doesn’t exist? I haven’t found so much information about it.

Thanks in advance,

PD) This is the function code.

function [lan_data] = lanread('montana.lan','C:\formato_lan')
% LANREAD Read Landsat data file type .lan
% Ex: im = lanread('montana.lan')
% size(im) = [m,n,d];
    % (From landsatdemo in the image analysis toolbox.)

% $Id: lanread.m 3325 2007-04-06 15:52:34Z finn $

if (nargin<2), thepath = []; end
if isempty(thepath)
  [p,n,e]=fileparts(which('fms150path'));
  thepath= {fullfile('.',filesep),...
            fullfile(p,filesep,'data',filesep),...
            fullfile(p,filesep,'data',filesep,'protected',filesep),...
            fullfile(p,filesep,'data',filesep,'protected',filesep, ...
                     'lan',filesep),...
            ''};
elseif ischar(thepath)
  thepath = {thepath};
end

fid = -1;
if (fid<0)
  for path_idx=1:length(thepath)
    filename = sprintf('%s%s',thepath{path_idx},lan_filename);
    fid = fopen(filename,'r');
    if (fid>=0), break; end
  end
  if (fid<0) % If not found anywhere
    error(sprintf('Could not open file: %s',filename));
  end
end

% find out how big the image is based on file size,
% assuming square image, 7 bands
nbands = 7;
fseek(fid,0,'eof');
file_bytes = ftell(fid);
nlines = floor(sqrt(file_bytes/nbands));
nsamples = nlines;

% skip header
nbytes_header = 128;
fseek(fid,nbytes_header,'bof');

% prepend * to read data into an array that has the same class as the data
A = fread(fid,[nsamples nlines*nbands],'*uint8'); 

fclose(fid);

% put data into a 3D array
A_3dim = reshape(A,nsamples,nbands,nlines);
lan_data = permute(A_3dim,[3 1 2]);

Answer 1

1. When calling a function (as opposed to defining a function) you do not need to use the keyword function. So, in order to use the function you just

   [lan_data] = lanread(‘montana.lan’);

2. When declaring the function, you must use the keyword function but with argument names. So the first line in file lanread.m should be

   function [lan_data] = lanread(lan_filename, thepath)
   

   and not

   function [lan_data] = lanread('montana.lan','C:\formato_lan')
   

   only when you call the function you use the values 'montana.lan' and 'c:\formato_lan' as arguments.

3. To get help you need to type exactly the function name

   doc lanread

and not landread