If you mean you have 1000 values stored in an array, and you want to change the stored values to be rounded to one decimal place, then you can do this:
Xround = round(X*10)/10;
[Edit: please note that if you have R2014b or later, there is a neater solution
Xround = round(X, 1);
as pointed out by ImageAnalyst.]
If you mean you want to print the values showing only one decimal place, then you can do this:
fprintf('%8.1f\n', X);
varying the format string as necessary to get the output you want.
If you mean you have 1000 different variables, perhaps with names like x0001, x0002 etc., then you should change the structure of your program, and store the values in an array.
