can anybody please tell me the use of 'val' function in this program.., it is not a valid function,yet the program can't be executed without using this,or by changing the function name.

% Load original 1D signal.
clc;
clear all;
close all;
ELEVATED=[]
[fname path]=uigetfile('*.mat');
fname=strcat(path,fname);

          load(fname );
         z=zeros(100,1);

         A=val(1,:)
         v1=val(1,:)-val(1,1)
         A=v1
         A=A'
         zc=A(1)
         A=[z;A;z]

        %  s = A(1:1:400);
          s = A;

          ls = length(s);
          figure(1)
          plot(s);
          title('Actual Signal'),grid on

    [c,l]=wavedec(s,4,'db4');
    ca1=appcoef(c,l,'db4',1);
    ca2=appcoef(c,l,'db4',2);
    ca3=appcoef(c,l,'db4',3);
    ca4=appcoef(c,l,'db4',4);

    figure(2)
    plot(c),title('decomposed signal'),grid on
    figure(3)
    subplot(2,2,1)
    plot(ca1),title('1st level reconstructed'),grid on
      subplot(2,2,2)
    plot(ca2),title('2nd level reconstructed'),grid on
      subplot(2,2,3)
    plot(ca3),title('3rd level reconstructed'),grid on
      subplot(2,2,4)
    plot(ca4),title('4th level reconstructed'),grid on

Answer 1

[Kye Taylor]

The lines

 [fname path]=uigetfile('*.mat');
 fname=strcat(path,fname);
 load(fname );

will load a .mat file into the scope of MATLAB environment. That .mat file must contain a variable whose name is val. You likely do not have the .mat file in the right place on your machine, if at all.

Answer 2

[Walter Roberson]

In the above, "val" is not a function: it is a variable being loaded from the .mat file.