Questions tagged [assignment]
For questions relating to assignments to symbols, patterns, or expressions.
253
questions
0
votes
0answers
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 ...
4
votes
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:
...
2
votes
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.)
1
vote
1answer
94 views
pure function assignment
I do not understand this statement from the Introduction to Dynamic tutorial:
...
2
votes
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 ...
2
votes
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:
...
0
votes
0answers
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 ...
1
vote
0answers
75 views
0
votes
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 ...
1
vote
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
...
2
votes
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
...
2
votes
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'...
1
vote
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:...
0
votes
4answers
64 views
1
vote
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 ...
0
votes
1answer
31 views
0
votes
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
...
3
votes
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
...
0
votes
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 ...
0
votes
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:
...
2
votes
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 ...
1
vote
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").
...
3
votes
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 $...
1
vote
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 ...
1
vote
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 ...
1
vote
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 ...
1
vote
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:
...
2
votes
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.
...
4
votes
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 ...
6
votes
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 ...
2
votes
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 *?
4
votes
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 ...
7
votes
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 ...
9
votes
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 <...
4
votes
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 ...
1
vote
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 ...
0
votes
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 ...
0
votes
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 ...
1
vote
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+\...
5
votes
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 ...
1
vote
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 <...
0
votes
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 ...
4
votes
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 ...
1
vote
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. ...
1
vote
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:
...
2
votes
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
...
8
votes
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:
...
1
vote
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[...
0
votes
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 ...
0
votes
2answers
151 views
Monte Carlo Method [duplicate]
How do you use a Monte Carlo method to approximate the area enclosed by the circle.
