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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4
votes
2answers
84 views

Limit won't compute

Does anyone know why the limit: ...
4
votes
1answer
67 views

Constructing an Array from typed expression

I want to produce an array from expressions given by test[one][1] = 3; . . test[one][5] = 7; etc. Normally would use ...
4
votes
1answer
118 views

DeleteCases vs. DeleteDuplicates for removing points within a critical Euclidean distance

I'm attempting to remove all points in an array which are within a Euclidean distance "ThresDist" of one-another. Using the command: ...
4
votes
1answer
98 views

How do you set an Optional parameter with a global variable on a Function defined in a Package

In a Package I am writing, I'm trying to define a function with an Optional parameter in it that is set to a global variable. ...
4
votes
0answers
105 views

Syntax error for optional pattern, but only in debugger

This expression (explained here by Leonid) evaluates fine unless Evaluation->Debugger is enabled: h[x : (_Integer) : 1] := x Syntax::sntxf: "x:" cannot be ...
4
votes
0answers
72 views

Is there a way to check whether two notebooks share the same variables?

When I code in Mathematica, I often re-use code from old notebooks which fulfilled a specific purpose; for example, one testing for soft matches in strings, or one that identifies outliers on a graph ...
4
votes
0answers
104 views

Proper treatment of roots and powers in Series?

I have the following problem in Mathematica 9 on Linux. I let Mathematica compute the Series expansion: ...
3
votes
5answers
372 views

Using variables in function names

I want to make a list of plots and my functions are named C1, C2... Cn. The command I wish ...
3
votes
1answer
90 views

Export file with semicolon at the end of line

Is there a rule that tells Mathematica to set a semicolon at the end of each line (except of the last one)? My MWE is: ...
3
votes
1answer
86 views

Syntax Coloring for “Possible Unwanted Assignment” Issue

Apparently Mathematica's syntax coloring engine believes that the second assignment in the following code excerpt (concocted for illustration purposes only) is a "Possible Unwanted Assignment" since ...
3
votes
1answer
141 views

Shortening the syntax {var1, var2} /. # & /@ list

I noticed that I often turn out to have a list of substitutions in the form ...
3
votes
2answers
113 views

How to define the irrational domain or any other arbitrary domain?

I have found no way to define the domain of Irrational numbers. I can easily define a test to see if a number is irrational by defining: ...
3
votes
2answers
294 views

Why does the first derivative of a piecewise continuous function have discontinuities?

I have this piecewise continuous function which is also continuously differentiable over time : ...
3
votes
2answers
101 views

Why does the iterator index in Table not work here?

I type the following command line Table[D[#1,varx[[i]]] &,{i,3}] where varx is a vector of dummy variables ...
3
votes
1answer
166 views

Using single replacement rule to convert algebraic expression

I have been trying this problems for hours and cannot find any helpful clues. How can I convert $Sinh[3\theta]+Sinh[\theta]$ to a rational function of x given $2Sinh[\theta] = x-x^{-1}$ by using only ...
3
votes
2answers
177 views

How to remove border points from InputForm?

I have this code, and it generates the below ListStreamPlot. The second graph is the ListStreamPlot overlaid with the points ...
3
votes
1answer
103 views

Force ellipsis to print an end of an expression

For pedantic reasons I want to display an infinite sum of fractions in fractional form (i.e. as 1/x not as x^(-1)) with an ellipsis at the end of the expression. I have tried a number of ways and ...
3
votes
1answer
305 views

Explanation on why Compile statement works only if input and output sizes work

I found the following code: Compile[{{m, _Real, 2}}, Fourier[m]][Table[N[i - j], {i, 4}, {j, 4}]] which doesn't work correctly. But the following was posted as a ...
3
votes
1answer
84 views

Differentiating a Dot Product

I apologize if this type of question has been asked before, but a preliminary search turned up nothing. I would like to differentiate dot products. For example, consider taking a derivative with ...
3
votes
1answer
344 views

What do the hashtags represent in the result of Solve, and how should I use them? [duplicate]

There is a function that I'm trying to get the inverse of. My function is a simple polynomial: Tn[T_] := 4/9 T^3/Tc^2 + 5/9 T Now I tried to find ...
3
votes
1answer
88 views

Dt acting on symbolic notational forms

This one must be simple, but I can't figure out a decent solution. Suppose, I have a symbol with a notational form applied to it, say OverHat[A]. Now, if I didn't ...
3
votes
1answer
57 views

Pathological behaviour when evaluating a sum

When I declare the function $f$ as follows: f[n_] := Sum[x/Sum[Sqrt[y], {y, 1, x}], {x, 1, n}]/n the input ...
3
votes
1answer
151 views

Levels and slots

I am struggling with levels and #, if I understand this I think I will be able to grasp the entire concept. ...
3
votes
1answer
124 views

Filtering the elements of an array to split them into two categories

So, I am new to Mathematica, and I am trying to write something that involves taking values from one array and separating them into two different arrays. My code for doing this is: ...
3
votes
2answers
85 views

Replacing a function in defined expressions

I'm having a little trouble with substituting functions into an expression. A minimal example is as follows: ...
3
votes
1answer
91 views

Why is ^^ff not the same as ^^ToExpression[“ff”]?

I want to convert a hexadecimal string to a decimal (base 10) number: 16^^ff 16^^ToExpression["ff"] The 1st line returns the correct answer of 255, while the 2nd ...
3
votes
1answer
101 views

How to make InverseFunction work on function defined with restriction on arguments

This example works to define InverseFunction on the first argument of a function ...
2
votes
2answers
498 views

Single dot textual form

How do I render a letter with a single dot above it? I see \[DoubleDot] and \[TripleDot] are readily available, but what about ...
2
votes
4answers
339 views

Using the result of Solve in subsequent calculations

I'd like to know how to use the results of Solve in later calculations. Here's what I'm doing now: This is my expression ...
2
votes
3answers
340 views

Matrix Multiplication in context of row and column vectors

I've been looking at some matrices in Mathematica and I've noticed something very weird: They're extremely temperamental when it comes to dot products! For example, if I have the following, ...
2
votes
4answers
152 views

Where did I go wrong with my implementation of finding a plane tangent to a surface?

I am working on finding the plane tangent to a paraboloid at a given point. My code: ...
2
votes
2answers
280 views

Write a function that returns the logarithmic derivative

How can we write a function that if we input an expression f, it returns the log derivative $\frac{1}{f} \frac{df}{dx}$. We have to use a conditional or pattern test so that the function accepts any ...
2
votes
3answers
802 views

Orthonormalization of non-hermitian matrix eigenvectors

When using Orthogonalize[] one can specify which definition of "inner product" is to be used. For example, ...
2
votes
2answers
125 views

How to make Mathematica returns the exact expression I typed

I'm using Mathematica to compare some constants. Before playing around with those constants, I would like to check that I didn't make any mistake in typing them. So my question is the following: "What ...
2
votes
3answers
370 views

Output of plots from within Do[ ] Command

I am wondering why the following does not plot the way it's written and exactly how does the Do[] function operate? I think I could be using it incorrectly. ...
2
votes
2answers
458 views

Superscript prime symbol

x\[Prime] looks like $x_'$, ugly right? Is there a way to make a symbol with prime to look like $x'$? That's what I'm trying right now: ...
2
votes
2answers
257 views

local variable naming & symbolic argument

I'm stuck here with my variable assignment in this scenario ...
2
votes
1answer
76 views

Is it possible to use a mathematical expression as function name?

This might seem as a silly question, but is it feasible to use a mathematical expression as the name of a function? For example, I'm studying the cross section of Compton scattering and there is a ...
2
votes
1answer
448 views

Indices and variable definitions in Mathematica

Does anyone know how I can do this in Mathematica? Just an example.. Defining indices and variables (defined over indices), "mapping" variables and indices: ...
2
votes
2answers
99 views

Is it possible to use infix notation ~ for functions with one argument or more than 2 arguments?

According to a Mathematica textbook, we can write N[x,n] by using infix notation as x ~ N ~ n. How about other functions with ...
2
votes
3answers
172 views

How do I interpret the following syntax?

I have been given some code with the following line PeriodicExtension[g_, x_] := If[Abs[x] < Pi, g[x], PeriodicExtension[g, x - 2 Sign[x] Pi]] I do not ...
2
votes
2answers
132 views

HoldForm[Operator ##] on some list

Recently in response to this question Mr.Wizard suggested an unusual way to summing numbers. This doesn't seem to be documented. ...
2
votes
2answers
129 views

Extracting counts of contiguous zeros and ones from a binary array

I'm a novice with Mathematica, but you guys have been very helpful to me in the past. I have a binary array [100, J repetitions] consisting of zeroes and ones. I'd like to extract a histogram of the ...
2
votes
1answer
184 views

Difference between Map[f[#] + g[#] &, {a, b, c}] and Map[f[x]+g[x]&, {a, b, c}]

Map[f[#] + g[#] &, {a, b, c}] vs Map[f[x]+g[x]&, {a, b, c}] My question is: why is the output different? ...
2
votes
1answer
191 views

What is an alternative to using backticks in separating namespaces from function names?

What is an alternative to the backtick (`) in separating the namespace from the function name? Can the function be called without using this symbol? I think in ...
2
votes
2answers
87 views

Return only one numeric solution to equation [duplicate]

Consider a simple plane equation 2x-3y+4z==7 I just want some position vector on that plane. For example, {7/2,0,0} would be ...
2
votes
2answers
193 views

Writing a function that returns a (usable) function

I am trying to create a function that returns Arnold's Cat Map of size n iterated k times. I can get something out of the Function command, but I can't figure out ...
2
votes
2answers
961 views

NMinimize with defined function call getting error NMinimize::nnum

I want to call the NMinimize function for my own defined calculations but I got an error. Below is a simple example. ...
2
votes
2answers
114 views

import a list of replacement rules

I have a text file with a set of replacement rules, of the form x^3y^2 -> 4, xy^2 -> 2, ... for example. I'm having some issues trying to figure out ...
2
votes
2answers
169 views

Manipulate, Import external table, save as CDF, mail presentation

For my work I do data analysis. Most of these analysis are done on big databases with milions of records. I would like to make a manipulate (or animate) using a external dataset and create a CDF ...