Oliver: I have used the keep function for years, but I have always thought it was poorly named. Matlab will always keep your variables unless you tell it to do something else with them. It took me years to find the keep function on FEX because I never searched for the word 'keep'. I still have the darndest time remembering the function name because my thought process is typically that I want to clear all variable except a few. In other words, clearing comes to mind first, and then I think about keeping. This function is intuitively named and can be found easily using Function Hints. That is, I can type "clear" and tab to find "clearnot".