Q:

how to save files in a loop in Matlab?

I have some geotif files and I am trying to create a mosaic out of them. I have tried to put the images beside each other first in a row and then tried to join the in columns and have the final mosaic. I would like to have the output file with the save number of the loop (outimage1,outimage2,..). I would like to know how should I introduce the output file with the sequence of the loop number. 
I would be happy if someone help me find my mistake in the following code.
 close all;
 clear all;
 clc;

 path = 'E:\MATLAB\...\tifs\';
 path2 = 'E:\MATLAB\...\tifs\out\';

 matfiles = dir(fullfile('E:', 'MATLAB',...,'tifs','*.tif'));

 files = {matfiles.name};
 lf=length(files);

 image_row = [];

 for L=1:11
     for k=1:14:lf
          fname = matfiles(k).name;
          fullname = horzcat (path,fname);
          infile = imread (fullname);
          image_row= [image_row,infile];
          [~, ~, ext] = fileparts(fname);
          outimage = fullfile( path2, sprintf('outimage%d%s', L, ext) );
          imwrite(image_row,outimage);
     end

 end

Yours assistant is highly appreciated. 

A:

I am not familiar with a matlab syntax k. format(fname).
If you want to do string formatting in Matlab - read this first.
A solution for your problem might be
 outimage = fullfile( path2, sprintf('outimage_%03d_%s', k, fname ) );

EDIT:
following comment by OP, get the file format (tif):
 [~, ~, ext] = fileparts(fname);
 outimage = fullfile( path2, sprintf('outimage%d.%s',ext) );

