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.

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3
votes
2answers
69 views

How can I adjust the global input variable of a function to the value of a local variable within the function

I am trying to define a function f[l_] that will perform an operation on whatever input variable I use (normally I use l which ...
3
votes
1answer
232 views

How to restrict global variables to within a given notebook? [duplicate]

Possible Duplicate: Is there a way to separate variables between multiple notebooks? I assigned a global variable like a=10; It works in all my ...
3
votes
1answer
54 views

Setting a One Dimensional Function Equal to a Constant over a Specific Range

I am trying to take the output from NDSolve and create a variable equal to the solution except for a certain range of values. Here is the code I am trying to use ...
3
votes
1answer
101 views

Need some explanation of “Global`*”

When I start a new notebook, I enter Names["Global`*"] I get this {"list", "msgs", "rhs", "z"} Then I enter, ...
3
votes
1answer
288 views

Evaluating a function on permutations of its arguments

Say I have a function "temp" of $n+1$ variables, $y,z1,z2,z3,...,zn$. I want to test if my function has certain symmetries like swapping $y$ with square of any $z$, swapping any two of the zs, ...
3
votes
0answers
89 views

What's reliable way of finding declared but undefined functions/symbols in several interrelated packages?

I have many packages some of which use some of others. I have many symbols defined in them. Is there a reliable way of finding declared/exported but undefined functions/symbols in several ...
2
votes
3answers
1k views

Better solution than returning a list of 3 values?

I have a function (using SetDelayed) that currently returns 3 values in a list. Later on I use the result of this list along with ...
2
votes
5answers
278 views

Treat list as cyclic

I am considering the following case. Say that T={p1,p2,p3} represents a triangle. In addition, I want to parameterize the edges of the triangle ...
2
votes
2answers
1k 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
229 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
3answers
289 views

Treat strings as variables?

I have a list of strings, {"x1", "x2", "x3", "x4"} And a list of linear equations: ...
2
votes
2answers
175 views

Local variables whose definitions depend on each other [duplicate]

Consider the following (pseudo-)function definition: f[l_] := Let[{ a = Length[l], b = First[l], c = b/a, }, c*10] So for ...
2
votes
2answers
348 views

local variable naming & symbolic argument

I'm stuck here with my variable assignment in this scenario ...
2
votes
1answer
117 views

Strange behaviour of variables in Table

I'm trying to work with some vectors and have run into a strange problem. An obvious way to define a difference of two vectors would be dif[x_,y_] := x-y I ...
2
votes
2answers
875 views

defining recursively a function with multiple if conditions

I am trying to recursively define a function which satisfies the following system of equations and which depends on two parameters $n$ and $l$, $$ \begin{align} A(x, n, l) &= F[ A(x,n-1,l) ]\\ ...
2
votes
4answers
306 views

Defining a General Complex Number

I am trying to compute the Complex conjugate of two complex numbers multiplied together. However, when I go to define my complex numbers as $a+b I$ and $c+dI$ it does not like $b$ and $d$ because they ...
2
votes
3answers
124 views

Extract memoized results in the form of a rule

Lets say I define a function f with memoization. Is there some way to extract the memoized values? For example, ...
2
votes
1answer
313 views

Define function that counts recursive fibonacci

If I write count=0; fib[0]:=(count=count+1; 0); fib[1]:=(count=count+1; 1); fib[n_] := (count = count+1; fib[n-2] + fib[n-1]); Then I can ...
2
votes
2answers
132 views

Extracting variables from Hold expression

For example I have some global assignments x=1;y=2;z=3 and an expression Hold[x*y/z]. How can I now extract variables ...
2
votes
1answer
105 views

Table of references [duplicate]

I have a list of variables (say a, b, c, d, e) that I want to assign in a single command. {a,b,c,d,e} = {1,2,3,4,5} would ...
2
votes
1answer
67 views

Is there a shorthand for Optional with Condition?

I have a recursive function that does some work to an object for a repeatedamount of times. ...
2
votes
1answer
128 views

Equivalent command to the Maple indets command

This carries on the discussion here and here. I had mistaken Variable[] to give you ALL variables in an expression, but apparently, it is not meant for that. ...
2
votes
1answer
59 views

Quoting definition explicitly

I'm trying to quote a definition using DownValues, OwnValues, etc. Everything seems to be fine, except for temporary symbols' ...
2
votes
1answer
97 views

What is the need for function parameters? Many possible inputs

If I have many possible variables related to one another, why do I need to define my function with parameters for plotting? For example, if I have an equation like: ...
2
votes
1answer
203 views

How to define a variable as a function of another variable?

I want to define a variable q which is a function of t. And I want to define another variable ...
2
votes
2answers
550 views

How to define a vector with automatically added symbolic elements with subscripts

I want to define a vector lets say k containing elements Symbolize[Subscript[k, 1]], k2, k3 ... etc. When I define lets say k4 . I want the symbol automatically added to vector k. Something like ...
2
votes
1answer
2k 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) ...
2
votes
1answer
80 views

Clearing a global variable from inside a Module

This is a highly simplified version of a initialization problem I have with a complicated program with many (about 100) modules. If one enters: X=42; Clear[X]; the ...
2
votes
1answer
514 views

How to define a matrix with all elements 0? [closed]

A matrix can be defined as M = Array[m, {3, 3}] which gives ...
2
votes
1answer
152 views

Reuse local variable in declaration within With [duplicate]

Considering the richness of Mathematica.SE, I am quite surprised I could not find my answer... I am very sorry if it is a duplicate. Consider the following example: ...
2
votes
1answer
43 views

Definition of a function depending on a sequence

let $a_{n}$ is a given fixed sequence, say $a_{n}:=1/n$. I would like to define something like $$D_{j}:=\sum_{k=1}^{j}\frac{1}{j!}BellY[j,k,\{a_1,a_2,\dots,a_{j-k+1}\}].$$ Function BellY is ...
2
votes
1answer
46 views

Strange behavior when defining a symbol/function pointwise

I am well aware of the fact that floating point number have finite precision, so one needs to be careful when comparing them. Still, I find it disturbing/surprising that the following input into ...
2
votes
0answers
37 views

Share variables among notebooks with different Kernels

So I have a server running in another notebook with a secondary kernel. I run my main notebook and launch the server notebook, but I have configured the variables in my main one, and can't find a way ...
2
votes
0answers
53 views

Changing variables in a series expansion

I want to compute the Taylor expansion of some pure function f[x_], but then perform a change of variables in the resulting expression. So, for example, the output ...
2
votes
0answers
60 views

Follow-up to “How to differentiate formally?”: Efficiency concern

In link to "how to differentiate formally?" and particularly to the answer by @Jens, I want to do something like this: ...
2
votes
0answers
25 views

Determining default value from previous arguments [duplicate]

How does one specify a default value for an argument which is dependent on the previous arguments of a function? For instance, consider the function ...
1
vote
5answers
168 views

Do not expand matrices in Mathematica calculation

Here is an example of a problem I'm having. Consider that I have defined: omega={{p[t]},{q[t]},{r[t]}} x={{a},{b},{c}} R={{1,2,3},{4,5,6},{7,8,d}} What I would ...
1
vote
3answers
169 views

How to replace element of list by index

I'd simply like to replace the value x at index [[j,i]] in a two dimensional table with the value ...
1
vote
2answers
106 views

Using AddTo in a function

I want to create a function that will take a variable $x$ and reassign the value $x+2$ to $x$. So f[x_]:= x += 2 However: ...
1
vote
2answers
163 views

Why does Evaluate[a[[1]]]=0 assign a value to a variable while a[[1]]=0 doesn't?

I'm trying to do a small page counter with Mathematica, for leting me know about my reading progress on some books. I'm stuck on a problem: ...
1
vote
3answers
482 views

Adding subscripts to variables

I know I can define vars = Map[Subscript[x, #1] &, {"tem", "pressure", "hum", "lat", "alt", "space", "corner"}] and ...
1
vote
1answer
71 views

Converting the subscript of matrix name to a variable

I want to change indices of matrix name during loop for creating different matrices. For example; ...
1
vote
3answers
174 views

Declare local variable when defining a function to mimic Table[]

The problem: I want to define a function tab to replace the long line Table[f[i,j,k,l],{i,3},{j,3},{k,3},{l,3}] by a shorter ...
1
vote
2answers
331 views

TabView: Reset some dynamic variable on tab selection

Given a TabView panel like this one TabView[{ DynamicModule[{x = False}, {Checkbox[Dynamic[x]], Dynamic[x]}], "foo"}] I ...
1
vote
3answers
2k views

How to create functions of arbitrary number of variables? [duplicate]

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 $z_2$? ...
1
vote
3answers
53 views

How to assign a variable name from imported file name [duplicate]

I have a set of files, e.g. file1.dat, file2.dat,... I want to do the following file1 = Import["file1.dat"]; where variable name ...
1
vote
2answers
159 views

Add a letter to a variable name from a list

Basically I am searching for a way to add the letter u to an existing list of variables {a,b,c,d} to obtain the variable list ...
1
vote
2answers
60 views
1
vote
1answer
60 views

Define operator with special characters [duplicate]

I have looked here which describes how to define operators. I was wondering whether there was a way to assign thes operators to special characters? eg Let $\odot:=(a+b)(ab),$ so ...
1
vote
3answers
82 views

Store matched variables

Edit: I am matching and replacing a particular expression. At the same time... I want to store matched variables for later use. I got it to work with messed up code involving ...