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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2
votes
2answers
711 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
117 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
3answers
185 views

How to make a defined symbol stay in symbol form?

How to make a defined symbol stay in symbol form? w = 3; g = 4; {w, g}[[2]] 3 I want the output to be ...
2
votes
1answer
189 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
109 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
85 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
3k views

setting a variable equal to the output of FindRoot

So I set a function f[x] f[x_] := x*E^(-x) - 0.16064 Then I set a variable 'actualroot' to the function FindRoot, starting at 3 ...
2
votes
1answer
85 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
50 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
93 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
2answers
426 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
2answers
129 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 ...
2
votes
1answer
132 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
128 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
0answers
20 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
3answers
826 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 ...
1
vote
2answers
94 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
159 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
398 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
991 views

How to linearize an expression automatically?

I would like to automatically linearize some long equations in the scope of variational calculus. Here follows an example of what I need to do : Given two variables $a_1 = q_1 + \delta q_1$ and $a_2 ...
1
vote
2answers
146 views

Define the square of a function [closed]

Is there any good way to define the square of a function in M9? Usually one can write e.g. f[z_] = 3*Sin[z] etc etc. But is it possible to define ...
1
vote
3answers
123 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
278 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
1k 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
2answers
135 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
3answers
75 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 ...
1
vote
1answer
138 views

Solving equations with QuantityVariable

I'm trying to understand how to easily solve equations that use QuantityVariable. Why does this fail? ...
1
vote
1answer
289 views

Generating a list of symbolic coefficients [duplicate]

I am trying to do something which I assume should be very simple: I want to generate a list with symbolic coefficients that looks like this: ...
1
vote
1answer
233 views

Print indexed (by subscript) variable name systematically

I have some variables : Subscript[S, 1], Subscript[S, 2]...etc. But they are defined in a for loop like For[g = 1, g < 4, g++, Subscript[S, g] = g]; Later, I ...
1
vote
1answer
452 views

How do I use a matrix that has a variable?

I seem to be getting an error whenever I try running this piece of code. Matrix12[n_] := {{1, 0}, {0, {\[Kappa]1[n]}/{\[Kappa]2[n]}}} I've already defined the ...
1
vote
1answer
336 views

How to substitute variables in interpolated function?

I'm looking for the way to substitute variables in interpolated function again to original one. (I want to know how to get P(r, theta) from Psol(v, w).) The original variables : ...
1
vote
1answer
75 views

Iteration convergence of Newton approximations

I am trying to determine for which initial values Newton's approximation of specific functions (EX: f(x)=x^2 -1)converge and to what numbers it will converge to. *Where Newton's approximations are ...
1
vote
2answers
564 views

How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc

I'm trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example, ...
1
vote
1answer
82 views

How to form a variable from matrix elements

I have matrix with n rows and 2 columns, say m = {{x11, y12}, {x21, y22}, ..., {xn1, yn2}. Now, I want to form three new variables for example: ...
1
vote
2answers
77 views

Calling variables with use of numbers in their names

I have got few huge matrices named by ascending numbers, e.g. x1, x2, x3,... and I need to do the same operation with all of them - to multiply their components, ...
1
vote
1answer
42 views

How to set the values into some variables from different lists [closed]

I have a list of Values and a list of variables. I want to set the Values into Variables. Assume the following code: ...
1
vote
1answer
180 views

Is linear interpolation applicable here

From my understanding about Linear Interpolation especially of that of Newton's Divided Difference Polynomial, we could get the value of F(x) from the given set of ...
1
vote
1answer
226 views
1
vote
0answers
106 views

How to create a complex variable from dated list values

Can anyone help me to construct a variable "PI" from values of variable x. Variable x represents a group of two time series rj and ri on equal dates(joined two dated lists with states).Variable x have ...
1
vote
0answers
104 views

specifying a list (vector) of arbitrary length

When trying to do symbolic calculations in mathematica involving a space of dimension n, which is arbitrary but fixed, I'd often like to work with vectors that have ...
1
vote
0answers
59 views

Telling mathematica that something is an integer [duplicate]

Is it possible for me to tell mathematica something is an integer? like if I typed Sin[n Pi]+Cos[n Pi] it would tell me it equals 1 for even n and -1 for odd n? ...
1
vote
0answers
72 views

Why the variable cannot use subscript? [duplicate]

Today,I use the Lagarange method to deduce the robot 's dynamic equation .I use the mma to help me calculate. I want to use $$x_B,y_B, v_{Bx}, v_{By}, v_B ^2$$ to represent the point B 's ...
1
vote
0answers
1k views

How to assign (and retrieve) variables with subscripts? [duplicate]

I like to give subscripts to my variable names when the variables are related. I.e., Subscript[r, i] = 3 3 A problem arises when I later assign ...
1
vote
0answers
158 views

Variable scope in nested NMaximize, NMaxValue

I'm trying to use NMaxValue inside other statements (FindRoot and NMinimize). Those statements should bind variable names, but I'm getting weird warnings which seem to indicate that the variables ...
0
votes
4answers
946 views

Specify a variable as an integer

I have a formula that always evaluates to a certain number for any variable X under one condition that X is an integer and ...
0
votes
2answers
115 views

Variable Value as Range

Thank you for the help so far! I would like to assign +/i signs for the function and solution such as (+)(+)(-) and therefore (-). It is working for the first evaluation, ╬╗lower, but not for the ...
0
votes
3answers
152 views

Clean-up Code / Reduce variables

I'm writing a playing card simulator of sorts, and everything works fine, but some Modules use a disgusting amount of variables. For Example: ...
0
votes
2answers
140 views

How can I assign some part of data from one list to another list?

I don't know this is correct question or not,but I have a doubt. I have two Lists names are list1 and ...
0
votes
1answer
55 views

How to specify the domain of a variable?

How can I specify for every expression the domain of a variable without using assumptions everytime i have to simplify it?