Can someone help me to explain/understand this code

if nargin==0, [file,pathname]=uigetfile('*.las');  else pathname=''; end;
if ischar(file)
fid=fopen([pathname,file]);
k=0; header=''; colblock=0; datablock=0; 
while ~datablock
jline=fgetl(fid);
if ~ischar(jline), break, end;
    header=strvcat(header,jline); 
if any(strmatch('~A',upper(jline))), colblock=0; datablock=1; end;
if colblock&any(strmatch('~',upper(jline))), colblock=0; end;
      if colblock & ~strcmp(jline(1),'#'),
         k=k+1; colnames{k}=strtok(jline);
      end;
if any(strmatch('~CURVE',upper(jline))), colblock=1; datablock=0; end;
end;
disp(' ');
disp(['Reading data for ' num2str(k) ' log curves from ' file]) 
data=fscanf(fid,'%f');
data=reshape(data,[k length(data)/k])';
fclose(fid);
data(data<=-999)=nan;
colnames=regexprep(colnames,'\W','_');
colnames=lower(colnames);
datastr.header=header;
for k=1:length(colnames)
datastr = setfield(datastr,colnames{k},data(:,k));

[Jan]

Please do not remove the question after answers have been given.

[Nisar Ahmed]

Hi Jan, OK

Answer 1

[Jan]

This code imports a text file and parses its contents. It does not contain any comments, therefore it is not useful for productive work. Without a documentation the readers have to guess, what its intention is.

Some commands are strange:

if colblock&any(strmatch('~',upper(jline)))

When searching for the character ~, there is no reason to convert the char vector to uppercase. Simpler and nicer:

if colblock & strncmp(jline, '~', 1)

Or in modern Matlab versions prefer startsWith(jline, '~').

strmatch, setfield, strvcat - this is an old code using deprecated commands.

The best way to understand, what the code does is to open a .las file and step through the code line by line during it is running. Simply set a breakpoint in the first line and use the Step-Button in the debugger.

[Nisar Ahmed]

Hi Jan,

here are ther comments.

%[DATASTR,DATA,COLNAMES,HEADER]=LOADINGLASFILE(FILE)
% Load LAS (Log Ascii Standard) formatted well log file
%
% FILE (optional): Input filename of file in LAS format.
% FILE should be character array within single quotes 'file'.
% Without input arguments displays dialogbox for file name.
% DATA: the numeric data matrix.
% COLNAMES: names of the columns as specified in file (cell array)
% HEADER: Header of the file as string matrix.
% DATASTR: Structure array containing HEADER and the COLNAMES as its fields.

[Walter Roberson]

if colblock&any(strmatch('~',upper(jline)))

That looks through upper(jline) to see if any of the characters in it are the ~ character.

if colblock & strncmp(jline, '~', 1)

That looks at the first character of jline to see if it is the ~ character. Not the same.

if colblock && ismember('~', jline)

would be better.