Questions tagged [assignment]

For questions relating to assignments to symbols, patterns, or expressions.

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26 views

Going between assignment rules and functions

I am trying to develop a model using Mathematica, and continuously run into difficulties going between the outputs of various functions (Solve, Differentiate, etc.) and back to functions (in the ...
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2answers
75 views

Assignment with Span to Indexed Variable

If I use span to assign a value to every element in a "column", it miraculously works: ...
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1answer
119 views

How can I list the common elements of two lists?

The elements of both lists are given as A={9,5,9,3}, B={9,9,5,5} In this case, how can I list the list {9,5,9} of the common elements of the two lists? (The order does not matter.)
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1answer
94 views

pure function assignment

I do not understand this statement from the Introduction to Dynamic tutorial: ...
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0answers
56 views

Certain plotting functions are setting variables unwantedly

I came across the following problem. Certain plotting functions set variables to values, which I do not want. For example, if I run SliceVectorPlot3D with an ...
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1answer
51 views

How can I transform equation results into an array of values? [closed]

I would like some help. I executed the following code: Solve[Det[(s IdentityMatrix[2]) - A] == 0] which yielded the following results at the output: ...
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51 views

Proper way to construct a function that takes too long to plot and integrate

Consider the functions phi[t_] and psi[t_] defined in the code below. These are used as basis functions for interpolation ...
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0answers
75 views

Fast definition of sparse tensor

I'm defining a sparse array through ...
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0answers
24 views

Extract actual result from equivalence [duplicate]

When I get a result like this {x -> -0.5 - 0.866025 I}, how do extract just the number: -0.5 - 0.866025 I. I can do this with the .rhs() method in Sagemath but I can't find the function in ...
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1answer
49 views

Why does the delayed functional assignment evaluate to `5=6`? [closed]

Why is it that x=5 x=x+1 nicely evaluates to 6, but the following ...
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0answers
56 views

Referring to matrices with index [closed]

For exampe I have two matrices, with index 1 and 2 Mat[1] = ConstantArray[0, {2, 2}] Mat[2] = ConstantArray[0, {2, 2}] I wanna assign new value with ...
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2answers
87 views

How can I get output from Reduce assigned to a variable? [closed]

I use Reduce to solve an 3rd order equation, and the output is given as the OR'd combination the solution variable. Normally, I can do a replacement to assign the value to a variable, but that doesn'...
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1answer
45 views

How to list automorphisms on a finite set and analyze them

Let s be a finite set of integer lattice points, for example s = { {0,0} , {0,3} , {1,1} , {0,2} }. I am trying to do two things:...
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4answers
64 views

Only Reals Rules

I have a huge array of rules with many variables, such as ...
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0answers
49 views

Errors with assigment and no errors with replacement rule, why? [closed]

So I have an expression, let's call it f11 which is a function of t of this form f11= a1*t^(-4)+ a3*t^(-3)+... and so on up until a finite positive power of t. In ...
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1answer
31 views

Using results from Nmaximize in loop

I try to Append the vector S by z+x whereby z and ...
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3answers
62 views

Assign value to the symbol returned by function

Ok, so here is example code: Clear[p, flag, k]; p = 2; k = 1; flag = True; If[flag, p, k] = 0; p After that I get the message ...
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2answers
121 views

Set value in a list at given position

Consider r = Array[Total[{##}] &, {3, 3}] (*{{2, 3, 4}, {3, 4, 5}, {4, 5, 6}}*) pos = {{1, 1}, {2, 2}}; vals={100,200} This ...
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2answers
75 views

Using a list as arguments in a function

This might sound a little silly question but I cannot get my code work. Here is the problem: I have quite a few lists of data which are basically beam profiles. I am using ...
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0answers
33 views

Setting paths of packages once and for all

My question is quite elementary: Each time that I want to load an external package package.m I have to run: ...
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1answer
55 views

Number of values stored in a function

Suppose I run this: f[0] = 1; f[n_] := f[n] = 2 f[n - 1]; f[1000] Now there will be 1001 values stored in f, and ...
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2answers
41 views

How can I use Part Assignment to change sublists into other sublists (without changing levels)?

Here's a 5x5 grid. Using predefined starting points, I'd like to change some sublists into something else (e.g., the values for a color, "drawing an opaque box"). ...
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3answers
378 views

Changing value of specific element in an array. (Converting code from MATLAB to Mathematica)

Can we change the value of a specific element of an array in Mathematica? Basically, I have the following given MATLAB script which writes a big 3N-by-3N matrix $h$ by combining two 3-by-3 matrices $...
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1answer
55 views

Scan and Set over multi-dimensional data

Suppose I have the following: Table[x[i,j] = f[i,j], {i,1,10},{j,1,10}]; I want to set variables x[i,j] to have value ...
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1answer
53 views

Default Options not working in user-defined function for SymbolName

Abstract I have a function objectName[symbol] that returns the SymbolName as both a standalone function or when nested inside ...
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1answer
59 views

Setting a function equal to another function then Clearing the latter

I have a loop in which several values of a function are computed, depending on the values for that function that were computed in the previous iteration of the loop. This could be implemented ...
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1answer
61 views

Set: in part assignment is not a symbol [closed]

This is probably a basic question but I am new to Mathematica, so please help me out here. I have the following piece of code: ...
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2answers
51 views

Cannot understand meaning of “identical”

This came up in the context of plotting solutions to NDSolve, but I've reduced it to the following issue. This really has me scratching my head. ...
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2answers
93 views

Using pure functions to assign a value to variable depending on whether it has been defined already

Let's say I want to assign to a variable the value $2020$ if it has not already been defined and do nothing if it has. In short, for a variable $a$, I want to achieve the functionality of ...
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4answers
217 views

Assigning a string to variables names

I have the list n1 = {{REL1, "REL.csv"}, {RAND1, "RAND.csv\"}}. That is {{variable name, string}, {name, string}}. I want ...
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1answer
41 views

Problem with superscript

I would like to know if there is option to make such scrpits like in this picture below. Is option to put letter instead of a *?
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1answer
99 views

Why the difference in performance? Array vs List and `Delete` vs `Nothing`

In a previous question I was warned against the use of Nothing to delete elements from a list, and rather use Delete. Being of ...
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1answer
103 views

How would you explain Nothing[] weirdness? [duplicate]

I would like to use Nothing[] to make some elements of a list invisible. (The intended use is to remove a few unwanted points from a ...
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1answer
131 views

Why Optional in Set is not held by the HoldFirst attribute?

When evaluatingf[x_:x0] := x, x0 will be evaluated, regardless of the HoldAll attribute of <...
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2answers
188 views

Using module to define a function that calls another function: Should i use set-delayed (:=) or set (=)

Suppose that I have a function f[x_,y_,z_]=x*y*z and now suppose I want to consider a specific application where z is a ...
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0answers
97 views

What does a single vertical bar mean in ConditionalExpression? [closed]

I got the condition below as part of a ConditionalExpression. Those single vertical bars before and after $\frac{1}{k1}$ appear to be an absolute value but I don't ...
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2answers
138 views

Assign FindRoot output vector to a vector instead of element by element

Using FindRoot to solve a multivariate equation system, assigning the output to variables one by one works, but assigning the output vector to a vector gives the ...
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0answers
28 views

Performing operations on LHS of assignment [duplicate]

Is it possible to first perform an operation on LHS of the = symbol, evaluate that, and then assign the RHS to the new LHS as usual? The following shows the most ...
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2answers
70 views

Assigning values to multiple variables from a list

I have a solution of the following form: $F(x)= \\ \qquad c+(x_0+x_1+x_2+\ldots +x_n)- \\ \qquad (x_0\,\log(x_0+\sqrt{x_0})+x_1\,\log(x_1+\sqrt{x_1})+x_2\,\log(x_2+\sqrt{x_2})+\ldots +x_n\,\log(x_n+\...
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1answer
112 views

Setting options of object after defining it

Is it possible to edit the options of an object like Plot or Graphics after I store it as a variable? For example, consider the ...
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2answers
68 views

Assign numerical values to symbolic variables in a vector inside a do loop

I have vector k = {k1, k2, k3, k4, k5, k6}. I would like to assign numerical values to the elements of k in each step of a <...
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1answer
99 views

How to turn a matrix into a 'function'? [duplicate]

I have some codes to turn a set of equations into a matrix. Suppose the matrix Lis expressed in terms of variables $\epsilon$, $K$, $M$, and I want to make a ...
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2answers
261 views

What is the point of tagset /:? [duplicate]

I'm teaching myself Mathematica and came across tagset. So I followed the example in the link, but seem to be missing the point. All of the below give me the same answer after assignment: that ...
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1answer
53 views

TagSetDelayed for spotting zero derivatives

I am trying to implement my own differential operator, d[arg_, var_], that computes the derivative of arg w.r.t. ...
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1answer
53 views

Part Assignment of variables with argument

I do not really understand why this: a = {1, 2, 3}; a[[1]] = 3; a {3,2,3} works as desired, but this does not: ...
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1answer
71 views

SetDelayed error for Derivative rule

Having a delayed assignment of the form Derivative[1][f][x_] := HoldForm[f[x]] works. But if there is a delayed assignment for f as in ...
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1answer
143 views

Error Message when nothing should be evaluated

When I try to define this simple function getCoeff[SeriesData[_, _, coeff_, _, _, _]] := coeff[[2]] I get an error: ...
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1answer
135 views

ContourPlot a list of equations generated by the Table command

The first command below produces proper contour lines while the second command produces an empty plot. I would think that the two commands should produce the same output. What's going on? ContourPlot[...
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0answers
27 views

Defining a function from an evaluated function stored in a variable

I have the evaluation of a function b, stored in appo. Now I want to define a new function f ...
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2answers
151 views

Monte Carlo Method [duplicate]

How do you use a Monte Carlo method to approximate the area enclosed by the circle.

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