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I often correct homework by checking the calculations in Mathematica. Sometimes you would like to have two solutions open at once. However often defined symbols such as f or phi regularly overlap between the two notebooks.

  • Is there a way to separate them other than using different symbols in every notebook?

  • Is it possible to separate some variables yet share others between notebooks?

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support.wolfram.com/kb/3664 –  Searke Mar 23 '12 at 18:22
    
@LeonidShifrin If I have two Mathematica workbooks that I would like to combine, is there a way to check whether they have any variables in common? Just like niklasfi, I often use symbols such as f in several documents. I was thinking of checking all the user-defined variables/functions in each of the documents, but I'm not sure how to do so. –  Vincent Tjeng Mar 26 '13 at 5:20
    
@VincentTjeng As far as I know, there is no automatic way. But it is possible to write a program that would do that. You can post this as a separate question, and I am sure you will get some good answers. –  Leonid Shifrin Mar 26 '13 at 10:36

2 Answers 2

up vote 43 down vote accepted

May be this, I have not tried it, but it sounds like this is what you are looking for (if I understood you correctly):

Evaluation menu -> Notebook's Default Context -> Unique to This Notebook.

So, you do the above for each notebook.

I found this in the daily Mathematica tip webpage: http://twitter.com/mathematicatip

Update

If you want to do it programatically from within a notebook, run SetOptions[EvaluationNotebook[], CellContext -> Notebook].

Update 2

To set this automatically for all new notebooks, open the Options Inspector (Ctrl/Command+Shift+O), and change the scope to "Global Preferences." Then, the option CellContext is found under Cell Options -> Evaluation Options. Change it to "Notebook."

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Is there a way to do this from within a notebook? e.g. calling a function like Quit? –  niklasfi Jan 28 '12 at 12:18
    
Is there a way to get Mathematica to set the context of new notebooks to be private by default, instead of having to create a private context for every new notebook manually? –  Joe Mar 6 '12 at 7:40
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@Joe Just looking for that myself. I added the info to the answer. –  rcollyer Mar 23 '12 at 17:29
    
Yes! Thank you @rcollyer, I've been looking for a way to do this for ages! –  Joe Mar 24 '12 at 9:21

Yes, there is. I recommend reading documentation related to Mathematica contexts. In a nutshell, all variables belong to some context (namespace), and all variables can be accessed via their fully-qualified names of the form "ContextName`varName". If you just use "varName", Mathematica will search contexts in $ContextPath (try evaluating the variable $ContextPath to see what it is), and will use the first context where it finds that variable. In addition, each notebook specifies a context (stored in the variable $Context) where all its variables are stored (unless fully-qualified name is used).

By default, for all notebooks the context is "Global`". Also by default, $ContextPath for all notebooks includes the "Global`" context (as well as "System`" and some others). The net result is that variables are shared across notebooks, and this can rather quickly become annoying. However, there's an easy solution. To create a "private" context for a notebook, evaluate the following:

SetOptions[EvaluationNotebook[], CellContext -> Notebook]

This notebook will be assigned a unique context (evaluate the variable $Context to see what it is). Also, global context will be removed from ContextPath (try evaluating $ContextPath before and after the SetOptions[...] above to see what's going on.)

[Update: As pointed out by rcollyer on the new Mathematica stack exchange, to set this option as the default for new notebooks, do the following: open the Options Inspector (Ctrl+Shift+O), change the scope (in the dropdown on the top) from "Selection" to "Global Preferences"; on the left expand the nodes Cell Options -> Evaluation Options, and change the CellContext setting to "Notebook."]

Now, here's how to create a shared context:

Begin["SharedContext`"];
varShared1 = "Shared string";
End[];

Alternatively, you could've just typed

SharedContext`varShared1 = "Shared string";

Now you can either use the fully qualified names ("SharedContext`varShared1" will work in any notebook), or you can add the context to $ContextPath:

AppendTo[$ContextPath, "SharedContext`"]

If you do this in all notebooks, varShared1 will become visible without a fully-qualified name.

To summarize, context work a lot like many other search paths. However, there are many subtleties (for example, if a symbol has already been defined in some other context, the Begin["SharedContext`"]/End[] block might not work as you expect -- the existing context of the symbol will be used instead of SharedContext`), so I recommend a healthy dose of experimentation and perusing the docs.

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6  
You can also set this via the Evaluation > Notebook's Default Context menu (instead of SetOptions.) [The documentation uses the "Unique to Each Cell Group" setting so that there aren't any variable conflicts.] –  Brett Champion Feb 4 '11 at 14:56
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Followup question: is there anyway to make Mathematica set the context of new notebooks to be private by default, instead of having to create a private context for every new notebook manually? –  Joe Aug 29 '11 at 7:16
2  
@Joe: Not that I know of, but I have written some convenience functions to easily set and access private contexts. I just type setPrivate[] when I start a new notebook, and spawnScratch[] when I want to duplicate the existing notebook's context in another notebook. I've used this for over a year and found it to be acceptably convenient. The code is here: github.com/leoalekseyev/mma-context –  Leo Alekseyev Jan 11 '12 at 23:10

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