How to load data without reloading?

I would like to load variables from a .mat file, but just those ones which are not loaded before. It is possible not overwrite the variables?

[per isakson]

Yes, see load(filename,variables)

Answer 1

[Chad Greene]

As I understand it, you have some variables in your workspace, let's call them x and y. You want to load some test.mat file that has variables x and y in them. You can do

x = 1; 
y = 2; 
t = load('test.mat'); 
x2 = t.x; 
y2 = t.y;

[Mr M.]

My problem is that I dont know I have x or not. Maybe yes maybe no. If I have x than I would like to load x, however in case of existed x I dont want to load x. And I want to do it automatically for all variables in the .mat file without knowing the names

[Chad Greene]

You can try

m = matfile('test.mat'); 
w = who(m);

to the get names of the variables in test.mat.

[Chad Greene]

Or, putting it all together, if test.mat contains a variable named x, load it:

if any(strcmpi(who(matfile('test.mat')),'x'))
    x = load('test.mat','x'); 
end

Similarly, you could compare the variables in test.mat to the variables in your workspace using ismember with who.