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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5
votes
1answer
225 views

How to convert an image to a compressed string representation equivalent to one copied to clipboard by `CopyToClipboard[image]`?

In my recent question I asked How to embed an image into a string? The suggested solution was ...
5
votes
4answers
162 views

Defining a function with parameters as variables

I have an expression V = (a[1] + a[2])b[1]. How would I define a function of a[1], a[2] and ...
4
votes
3answers
200 views

Is it possible to make the Button execute two or more actions?

According to the help: Button[label,action] Is it possible to make the button execute two actions?
4
votes
2answers
364 views

List reversion inspired by Python

In python, if you wish to reverse a list, here is the trick: range(10)[::-1] => [9, 8, 7, 6, 5, 4, 3, 2, 1, 0] Note: ...
4
votes
2answers
192 views

How can I avoid getting the error message Goto::nolabel in my code?

If anyone could suggest a reason why Label[begin] ... Goto[begin] would return Hold[Goto[Begin]], and (better) how can I avoid ...
4
votes
3answers
277 views

Brackets in output make unable to use output to identify matrix element

I'm trying to write a code where each matrix element swaps with a randomly selected neighbor (cardinal directions only) to redistribute the matrix. So far I've been able to replace an element with its ...
4
votes
3answers
644 views

Integrating with multiple indicator functions

I am trying to calculate an integral involving multiple indicator functions, such as: $$ h(u,v,w) = -\int_0^1 J^{\prime\prime}(s) (I_{(0,s]}(u) - s)(I_{(0,s]}(v) - s)(I_{(0,s]}(w) - s)\, ...
4
votes
1answer
171 views

How to see abstract syntax tree of Wolfram Language expression

I mean, suppose I have this expression: 2 + 2 I want to get something like this: Plus[2, 2] as an output. I've tried FullForm, but this just evaluates 2+2 and returns 4. Is this even possible?
4
votes
1answer
74 views

Dot when used in a pattern becomes Times… Why?

In[1] := Hold[a.b] // FullForm Out[1] := Hold[Dot[a,b]] So far so good. ...
4
votes
2answers
232 views

Can someone explain this code for joining two lists by the first element of each sublist?

Background (which may be skipped, unless context is needed) I've recently begun learning Mathematica (and only up to chapter 3 of Wellin), but wanted to write some code to get a better feel for ...
4
votes
1answer
109 views

Setting a binary operator Flat

I defined a binary operator in as the first statement in a new Mathematica notebook. {x1_, y1_} ⊕ {x2_, y2_} := Module[{}, Print["do anything"];] where the code ...
4
votes
2answers
239 views

How can I compare the previous value and the current value implemented during NestWhileList?

I am trying to write a part of my code. I am using NestWhileList. However, I couldn't find out the right syntax for testing. It should compare previous result and current result and continue if it is ...
4
votes
2answers
74 views

Why can't I pass in a product of matrices in my modified matrixform? [duplicate]

In attempt to build a function that would work like MatrixForm but would wrap a matrix with brackets, I tried the following function: ...
4
votes
1answer
249 views

Upon opening my notebook, I must evaluate cell for code to work properly

I am new to Mathematica. Once I evaluate the cell containing the code, my Manipulate works as desired; however, if I open the file and do not evaluate the cell, the Manipulate goes haywire. Can ...
4
votes
1answer
310 views

Path queries for tree-structured data

Can anyone suggest documentation or tutorials for developing path queries and indices for (XML-like) tree-structured data? Suppose data is organized hierarchically in key->value pairs, eg: ...
4
votes
2answers
215 views

Scalar product operator of complex vectors

What is the scalar product operator for complex vectors (or matrices) in Mathematica? The usual $Dot[]$ doesn't work. E.g. here is what the Mathematica gives $$\{1,0\}.\{I,0\}=I$$ but the answer ...
4
votes
2answers
102 views

Limit won't compute

Does anyone know why the limit: ...
4
votes
1answer
74 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
719 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 ...
4
votes
1answer
136 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
105 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
2answers
139 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: ...
4
votes
0answers
189 views

Do any mainstream text editors support Wolfram Language syntax for highlighting?

Syntax Highlighting for Mathematica on a Blog There is the above, but I'm not terribly excited to install rogue packages. For example on github, I share lots of Mathematica code. I see no way to ...
4
votes
0answers
135 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
84 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
109 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
515 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
2answers
661 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 ...
3
votes
3answers
701 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: ...
3
votes
3answers
143 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 ...
3
votes
1answer
99 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
90 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
170 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
336 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
152 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
114 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
210 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
1answer
75 views

Highlight the same symbol throughout notebook

Once I saw people using Matlab use a keystroke shortcut that made all the same symbols as a selected symbol become blue. I am wondering is there is a function in Mathematica that is similar. If so, ...
3
votes
2answers
199 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
107 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
336 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
109 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
103 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
62 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
180 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
129 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
1answer
101 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
106 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
4answers
423 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
1k views

Orthonormalization of non-hermitian matrix eigenvectors

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