Questions on correct (or improved) formulation of Mathematica code to achieve particular results. Use this tag (not "symbol") for questions about all those odd @@ /@ # & and ~ characters.

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0
votes
1answer
35 views

Full superset not displayed on Manipulate slider

I wish to incorporate ODE solution with Bondary condition sets: ...
0
votes
1answer
189 views

Getting “Null” output from package?

I have a script written to test a package as follows: ...
0
votes
1answer
79 views

How to write series of Do[ ]'s with a single Table[ ]?

Edited to provide more information (sorry I don't know how to format matrices here) I would like to replace: m = 4; ...
0
votes
1answer
139 views

Holding Input Windows

I am creating a Mathematica document which contains a list of proofs in various fields of Mathematics so that I can easily review whenever I would like. First, I create a large set I call 'proofs' ...
0
votes
1answer
89 views

Plot producing many error messages when given complicated function

I'm new to Mathematica and am running in to all sorts of silly difficulties with coding in it. I'm trying to calculate a function f[x, k], normalise it with another ...
0
votes
1answer
200 views

Pattern match with Table for matrix dimension check

In Mathematica, often an expression involving matrices will encounter dimension mismatch errors, like we are multiplying a 3x2 matrix to a 3x4 matrix. Below we define a new symbol Dim, which can be ...
0
votes
1answer
205 views

How to generalize a formula?

This is a piece of my code: ...
0
votes
1answer
50 views

A question about the syntax [closed]

I have $3$ elementary questions to ask and I thank you in advance. Question N°1. What is the right syntax for $$y\equiv0\pmod {2}$$ in the code below? ...
0
votes
1answer
36 views

Testing Conditions in For Loops

I am attempting to create a set of coefficients that satisfy a set of conditions using the Do function and If statements. I did this successfully with a basic set of conditions: ...
0
votes
1answer
184 views

How To Use D[ ] to Define a System of PDEs

We have two variables $u_{1}$ and $u_{2}$ which are functions of $x,t$. That is, $u_{1}=u_{1}(x,t)$ and $u_{2}=u_{2}(x,t)$. Consider the the system of partial differential equations $$\frac{\partial ...
0
votes
1answer
51 views

Block Matrix Multiplication [closed]

I have a = {{-1}, {0}, {0}} b = IdentityMatrix[3] c = {a, b} d = {{7}, {2}, {0}, {0}} and would like to compute e = c.d ...
0
votes
1answer
61 views

NDSolve emitting dvnoarg error [closed]

I'm trying to solve this simple system of ODEs, but it gives me the error "The function v1 appears with no arguments". I've attached a screenshot of the code. I hope someone could help me, I really ...
0
votes
1answer
38 views

How to get array/list of results of RotationMatrix?

For most other functions, passing in a list of arguments will return a list of results. E.g. t = Range[0, 10]; m = N[Sin[t]] returns ...
0
votes
1answer
60 views

While Loop Not Looping [closed]

no matter what I do, the following function always returns the first v. This does does not make sense to me at all. It should loop and reevaluate v and only stop when v matches the condition. What am ...
0
votes
1answer
66 views

Combining functions - is this a case for Piecewise?

I have a function $Eb1$ which was the subject of a question I asked recently - you can see it here on stack exchange. Now, in that example it's specified between a boundary $r_n$ and $r_o$ where $r_o ...
0
votes
1answer
198 views

Issue with Compile

The following code works fine with the the function f defined as a module, however, when I convert it to be a compiled function, it gives me errors. Can some one ...
0
votes
1answer
65 views

Convert variable into function

Sorry if this is a duplicate, but I have a variable called H. H is some complicated function of ...
0
votes
0answers
48 views

memory aid frequently used commands [on hold]

I am looking for links to a summarized list of most used commands of Mathematica or a reference manual with examples that only includes commands and syntax. I would also like a list of keyboard ...
0
votes
0answers
45 views

Treating expressions as symbols [duplicate]

I'm trying to do something like this: test = {x, y}; With[{test[[1]] = 3}, x/y] However, the following error is printed: With::lvset: "Local variable ...
0
votes
0answers
33 views

What does this “Cos[1.theta]”mean in Mathematica? [duplicate]

{{u[theta] -> 2.22328*10^8 - 2.22328*10^8 Cos[1. theta]}}
0
votes
0answers
31 views

What does a single @ do? [duplicate]

I have a simple expression: N@Log2@g[2048] I understand that N is Numerical value , that a function called g is being ran with 2048 as its first argument. But ...
0
votes
0answers
33 views

Assigning to a variable with a computed name [duplicate]

I wish to assign about a dozen variables to complicated expressions. to ensure that the correct variable is assigned to the correct expression, I’d like to do something resembling ...
0
votes
1answer
50 views

Help for properly writing simple derivative expression

I need help to write the following expression (only 1 iteration): f(x) = ...some basic function... f[X0,...,Xp] = f(p)(x0) / p! What I have so far: ...
0
votes
1answer
62 views
0
votes
1answer
70 views

Position of elements in a list satisfying some criteria - Understanding the syntax [closed]

From this post: if one wants to know the position of the elements of a list that satisfy some criteria, (s)he can do something like that: ...
0
votes
0answers
42 views

How can I mix // with a function of two arguments? [duplicate]

I often find myself using // when playing around with expressions, but it is always cumbersome to have to switch to the full notation just to apply a function of ...
0
votes
0answers
79 views

My “N” turned red randomly [duplicate]

For some reason my N function showed up in red even though I haven't noticed it in that color before. The color actually makes the code much more readable but I just don't know if I should be alarmed ...
0
votes
0answers
117 views

Meaning of backtick in conjunction with units [duplicate]

In this fragment from an equation solution the backtick is used twice: ...
0
votes
0answers
63 views

TableDirection in TableForm

I got confused about what does "the outermost dimension" and "the first dimension" mean in the document I snipped. Does it mean row or column?
0
votes
0answers
44 views

Using Table[ ] vs using Do[Append [ ] ] [duplicate]

Is it generally better/faster to use the Table function over using Do[Append []]? For example, I have this piece of code: ...
0
votes
0answers
21 views

Incorporating Built-In Function Options/Parameters into Shorthand [duplicate]

Shorthand syntax provides an alternate way to apply functions and, in many cases, improves readability. A simple example would be ...
0
votes
0answers
145 views

The /. syntax in numerical methods [duplicate]

I have an analytical approximation method for solving an ODE and want to compare this to an NDSolve solution, but the syntax is confusing me. To get the solution from NDSolve, I define the ODE as eqn ...
0
votes
0answers
186 views

Assigning numerical values to constants results in complex coefficients in Equations of Motion

I am using Mathematica to get the Equations of Motion (EOM) for a mechanical system (using Lagrangian Mechanics). While I get the EOM in symbolic form, on introducing the following code for assigning ...
0
votes
1answer
96 views

Why does Eigenvalues[matrix I defined] not work? [duplicate]

This is the code I have in my mathematica notebook. I want to find the eigenvalues of the matrix I created called Hmatrix as defined below. However when I type Eigenvalues[Hmatrix] I get the Hmatrix ...
-1
votes
2answers
93 views

How to make sure input is an ODE

I'm having trouble wrapping my head around why this isn't an ordinary differential equation. ...
-2
votes
1answer
64 views

Sign of a symbolic expression as a function of parameter values

I need to know the sign of the following expression for p[t] = z/(1-a), as a function of the parameters {a, b, c, z}: ...
-4
votes
0answers
65 views

How to define this function in Mathematica? [closed]

Q set of rational, Q' set of irrational Determine $F+G$ , where $F(x) = x^2$ when $x \in Q$ and $-x^2$ when $x \in Q'$ $G(x)= {(2^{1/2},4),(7,0),(3,8)}$
-5
votes
1answer
344 views

Split dataset based on the first column [duplicate]

I have a dataset which I want to split based on the first column. The data looks like this ...