Questions on assigning and unassigning definitions to names that represent them, including issues raised by context and localization. Use tag [assignment] for issues relating to Set versus SetDelayed.
60
votes
7answers
2k views
What are the use cases for different scoping constructs?
Mathematica includes three functions that I know of which can be used to effectively (if not actually) define a variable and give it a value within a local scope: ...
15
votes
5answers
3k views
How do I clear all user defined symbols?
Is there some way to do this other than going to Evaluation -> Quit kernel and firing a new one up?
12
votes
4answers
937 views
Clear complains that a variable is not a symbol or a string?
Here's a small listing where I've used EscqEsc to typeset θ in the notebook:
...
7
votes
3answers
378 views
Elegant manipulation of the variables list
I have a list of global variables (some of them are indexed variables), for example:
varsH = Hold[U0[1], U0[2], B0, V0[1], V0[2]]
Or (if it is easier to handle) ...
12
votes
4answers
425 views
Making a symbol's new definitions be tried before all previously defined ones
Is there any way to "close" a package (or a symbol, or a context) in that if a user of the package adds definitions to the symbol they will be tried before the package defined ones, just like what ...
5
votes
3answers
539 views
Assigning values to a list of variable names
As part of a calculation I need to do something like this
Evaluate[{aaa, bbb, ccc}[[ index]]] = {1, 2, 3, 4, 5}
so if index is ...
14
votes
3answers
397 views
Create an adaptive amount of local variables for error propagation
I intend to write a function which calculates the result and the error for any formula with any amount of variables using the Gauß Error Propagation.
The error $dR$ for a function $R(a,b,c)\,$ and ...
11
votes
7answers
482 views
How to Set parts of indexed lists?
I would like to assign a list to an indexed variable and then change it using Part and Set like this:
...
30
votes
3answers
667 views
Why modules with no variables?
I was reading some code, in particular, recipe 4.13 on unification pattern-matching in Sal Mangano's Mathematica Cookbook, and there were many instances of Modules with no variables in them, such as
...
1
vote
3answers
215 views
How to create functions of arbitrary number of variables?
In the following code what would be the simplest way to generalize it to say some $N_f$ number of $z$ instead of just $z_1$ and $z_2$?
...
27
votes
3answers
648 views
Is there an equivalent of MATLAB's Workspace window in Mathematica?
For example, in MATLAB, a panel is available where one can see straightaway which variables are used and their dimension sizes. Is such a feature available in Mathematica? I really find it hard to ...
4
votes
3answers
277 views
How to Clear variables with apostrophe?
An apostrophe ' is often used when we want to distinguish two variables. For example, if we already have a variable t and we may ...
2
votes
1answer
458 views
Constructing variable names from a string
I have groups of descriptive variable names and dont want to write explicit code for each group, e.g. (and this is a contrived simplification)
...
10
votes
3answers
226 views
How can I hold UpValues but evaluate other expressions?
Consider these definitions:
own = "OwnValue";
down[_] = "DownValue";
sub[_][_] = "SubValue";
N[n] = 3.14;
_[___, up, ___] ^= "UpValue";
The attribute ...
2
votes
1answer
183 views
Can I create a dynamic number of rows in TabView through an iteration?
I have written code, with the help of stackoverflow of course, and I want to make it user friendly so that other people in my lab can use it. I'm playing with DialogCreate and similar functions. I ...
14
votes
6answers
882 views
Why can't I define vector v as having subscripted elements v_1, v_2, v_3…?
I'm a very beginner in Mathematica 8 programming. While trying to play a little with tensor analysis I encountered a problem. How to define for example vector in such manner:
v={$v_1,v_2,v_3$}
For ...
10
votes
4answers
247 views
How to use pattern matching to assign values to Subscript[f,x_]?
I want to define two subscripted functions Subscript[f,1] and Subscript[f,2]. To keep the assignments local, I would like to ...
9
votes
4answers
357 views
how to differentiate formally?
I have been wrapping my head around this for a while now and I have not found a solution so far.
I want to work with an arbitrary number of variables in mathematica and use some built in functions.
...
12
votes
6answers
333 views
How to clear all variables except one?
I have a lot of variables: $a,b,c,d, \ldots $
I want to clear the values of all of them except $b$. It's really lengthy to write
Clear[a];
Clear[c];
...
Is ...
8
votes
3answers
313 views
Variable variable names
I have two variables, $ u \in \{0,40\}$ and $\gamma \in \{0,1\}$. I take $10$ values of $u$ and $5$ values of $\gamma$ and using their combinations as a pair of input parameters, I perform some ...
8
votes
3answers
222 views
Problem when defining variable in Mathematica
I'm trying to run this:
domain := {n, 0, 10};
Plot[n, domain]
but it doesn't work. Instead, it generates the message
...
6
votes
4answers
539 views
Define a mathematical set
I have a terribly short question:
Is there a way to define a pure mathematical set?
I tried a bit of googling, but the word "set" has two meanings and the other one (as in setting) as by far more ...
5
votes
5answers
331 views
Using a built-in symbol as a variable
I want to produce a Mathematica Computable Document in which N appears as a variable in my formulae. But N is a reserved word in ...
2
votes
2answers
265 views
Global variable initialization in packages
Is it a good idea to Initialize variables globally inside a package ?
will they be local by default to that package ?
2
votes
3answers
144 views
how can I generate a sequence of assignments?
I want to make a sequence like follows
r[1]=
r[2]=
r[3]=
r[4]=
....
r[n]=
The above r[i] represents coordinates which I have ...
2
votes
2answers
189 views
local variable naming & symbolic argument
I'm stuck here with my variable assignment in this scenario
...
