Is there a way to clear everything before starting in Mathematica?

Question

In MATLAB there is the function clear to delete all current variables. This is very useful if you start something totally new and don't want to get conflicts with earlier calculations. I'm searching something similar for Mathematica now, but I couldn't find anything except of Clear[VAR] which removes only the variable VAR.

Answer 1

You can use ClearAll to clear the variables and their attributes in your Global context (default) like so:

ClearAll["Global`*"]

If you're working inside a different context (e.g., notebook specific context or cell group specific context), you can do

ClearAll[Evaluate[Context[] <> "*"]]

If you want to remove all symbols from the kernel so that Mathematica doesn't recognize them anymore, you can use Remove[] similar to the above two examples.

Barring these, you can always quit the kernel with Quit[] which will remove all symbols. A fresh kernel will be initiated the next time you evaluate something.

Answer 2

I recommend one of two methods:

1. Keyboard shortcut to Quit[] the kernel

There is a system file KeyEventTranslations.tr that you can edit to customize keyboard shortcuts. I, as others, have added Ctrl+Q to Quit[] the kernel, allowing for a rapid clearing of all sessions variables. For more information on setting this up, see:

• Customizing Mathematica shortcuts

2. Give the new Notebook a unique context

In Mathematica, the current $Context defines what Context unqualified symbol names belong to. By giving a new Notebook a unique Context, which is easily done through the Evaluation menu, the symbols used in that Notebook will not collide with unqualified symbols in other Notebooks. See the following question for more detailed information:

• Mathematica - Separating Notebooks