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
1answer
96 views

How to localize symbols on the right-hand side of Rule when using ReplaceAll? [duplicate]

I am frustrated by the following: {1, 2, 3.0} /. a_Integer -> a + 1 The a on the left side of the arrow is localized and ...
3
votes
2answers
139 views

Using a variable for two different purposes

I want to name a bunch of tables after the OEIS entries which describe them. Is there any way to use these names for both the table name and the link at the same time? The second line uses the ...
3
votes
2answers
164 views

Bare symbol invocation fails but not if used with an argument

How to achieve the following behavior on a symbol f? Background: The main goal is to use the symbol to tag an abstract data structure where downvalues are used to store information. Only defined ...
3
votes
1answer
117 views

Is it safe to assign a variable and function of the same name for different things?

I'm writing out a notebook that goes through the van der Waals Equation of State for gases, and I run into a situation where I want to assign (simplified) Tc[b_]:=5b, use that to solve for b in terms ...
3
votes
1answer
73 views

plotting after solve does not display anything

I'm quite new to Mathematica language, I am trying to figure out where I am making mistakes in Plotting a specific function that depends to other variables: I want to plot ...
3
votes
2answers
73 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
239 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
58 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
110 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
297 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
78 views
3
votes
0answers
90 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
2k 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
294 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
3answers
237 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
299 views

Treat strings as variables?

I have a list of strings, {"x1", "x2", "x3", "x4"} And a list of linear equations: ...
2
votes
2answers
184 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
367 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
907 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
3answers
70 views

How to make a list (of data points) whose name is the same as the file name from which the data is imported [duplicate]

I have a set of files, e.g. file1.dat, file2.dat,... containing data (list of data points to plot, manipulate...) I want to do the following ...
2
votes
4answers
315 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
129 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
352 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
137 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
107 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
73 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
142 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
61 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
99 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
218 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
581 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
88 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
733 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
158 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
45 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
50 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
46 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
60 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
61 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
170 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
235 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
111 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
167 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
2answers
51 views

How do I tell if a function definition “contains” a symbolic expression?

Consider a definition like f[x_] := x[[1]] + x[[3]] + x[[1 + 2]] I want a "ContainsExpression" which I can use similarly to ...
1
vote
3answers
503 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
96 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
183 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 ...