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21
votes
3answers
492 views

Real Numbers in the Wolfram Language

Epilog: Much of the discussion in the answers below revolves around the distinction between Real as a data type and real numbers as a domain or class of numbers (irrespective of the form in which ...
0
votes
1answer
179 views

How do I write nested for-loops?

Looking through the reference.wolfram, I couldn't see an example of how to write a multiple line "for" loop in Mathematica. I need to nest many for-loops in such a way I can do many things in the ...
4
votes
2answers
390 views

Code elegance and compactness. Help needed with Map, Apply

I need some help with code optimization and compactness. I have a set of two-dimensional points and I can use the Mathematica function FindClusters to find 4 clusters. I'd like to plot the points ...
2
votes
0answers
59 views

What was the thought behind the parallel versions of Table, Map, etc..?

There separately named versions of the parallel analogues of Map[] and friends: ...
2
votes
3answers
119 views

Computing a sequence by recurrence

I am trying to create a list where each element of the list is calculated using the sum of all previous elements of the list and also uses the $N$th element of another list. The initial value of the ...
1
vote
1answer
76 views

Computing a Sequence using Recurrence

I posted a similar question earlier today, but unfortunately I realized after several hours that I over-simplified the problem for this forum. There is a very good answer to the Computing a sequence ...
10
votes
2answers
335 views

When must I use the Return function?

In a comment to my answer to this question, QuantumDot asks, "Where can I find more information on when I must use the 'Return' function?". I found this too deep a question to be answered by leaving a ...
20
votes
1answer
270 views

M9 performance regression for Fold?

Bug introduced in 8.0 and persisting through 10.0.2 or later I noticed an over 10x performance drop on Mathematica v9.0.1 (as Oleksandr R. commented, also v8) compared with v7.01 for this code: ...
2
votes
2answers
101 views

DictionaryLoopkup - pattern specification

I would like to find all Italian words that have a specific pattern of letter repetitions. Actually I'm looking for 6-letters words that have 1 letter repeated 3 times, a second letter repeated two ...
3
votes
1answer
161 views

How can I trans-compile Mathematica into another language?

I'm looking for an exhaustive list of source-to-source compilers to all other languages, if any exist that is.
5
votes
1answer
102 views

Changing the definition of N: unexpected $RecursionLimit::reclim error

I have some objects represented as follows: Object[data, param] data is a list of numbers, ...
74
votes
3answers
3k views

How to make use of Associations?

I have been curious about it for long. Now that Mathematica 10 arrives, I think it's time to ask the question: How the new Association data structure would be used ...
4
votes
1answer
40 views

How to find out which definitions use Temporary symbol?

According to the Documentation, Symbols with attribute Temporary are automatically removed when they are no longer needed. For example: ...
14
votes
3answers
203 views

How do I understand ListCorrelate(contains $\{k_L,k_R\}$) when it works for 2-dimentional data?

Two months ago, I asked a question here And @nikie give me a solution: The intuitive way to understand ListCorrelate is that the kernel is "moved" to every ...
1
vote
0answers
71 views

Concise way to express Table[FactorInteger[300][[n, 2]], {n, 1, Length @ FactorInteger[300]}]

I can get the exponent part of FactorInteger[300] with Table[FactorInteger[300][[n, 2]], {n, 1, Length @ FactorInteger[300]}] ...
35
votes
4answers
598 views

What's the difference between Inactive and HoldForm?

In version 10, Mathematica not only added Inactive / Activate but also highlighted this change in the "New in 10" page (in Core ...
3
votes
2answers
102 views

MapThread problem

I would like to do the following: ...
2
votes
0answers
59 views

Unexpected behavior from Indexed

I was going to include Indexed in this answer, thinking that it operated much as a List-only ...
0
votes
1answer
63 views

What does this Append expression do? [closed]

I have to understand some code. A part of it is written below. Can someone explain to me what it does: ...
9
votes
6answers
371 views

Product of elements of a list

Sum is for functions; Total is for a list. Product is for a function; what is the command ...
9
votes
2answers
122 views

DownValue assignment using Apply

Why does assigning a DownValue using Apply, e.g., ...
2
votes
0answers
31 views

How exactly does ReplaceAll work? [duplicate]

I am not sure if this question has been asked before but anyway, Consider these two examples: ...
5
votes
4answers
193 views

Signed power set of a list

Given {a, b, c, ...} with $n$ elements generate a list with $2^n$ elements. For example, if the list were {a, b, c}, then the ...
0
votes
0answers
90 views

Solution of a set of quadratic congruences (Chinese remainder)

Edit: Please remove this question. I think there are mathematics error in what I am asking. You are welcome to edit the question if you can state the problem correctly. I have a set of quadratic ...
2
votes
1answer
286 views

Dynamic graph construction and visualization (Watts' “Small Worlds” α-model)

I need some help in creating a Mathematica program for building and visualizing Watts' "Small Worlds" α-model. This is a variant of the more known (and much more simple) β-model (also known as ...
5
votes
2answers
146 views

Non sequitur in documentation of MemberQ

Mr.Wizard's question about MemberQ and FreeQ got me to re-read the documentation for those functions. I find I don't understand ...
0
votes
1answer
71 views

Association of pure functions [duplicate]

I've encountered confusing behavior of Association when I try to use it for storing pure functions. For example: as = <|"1" -> # + 1 &|> ...
9
votes
5answers
485 views

Postfix Double Slash Notation with Multiple Parameters [duplicate]

Examples A convenient shorthand that I use frequently is the "double slash" notation to string commands together. For example, I can write: ...
11
votes
2answers
217 views

How to restore function attributes to default

Adding an attribute to a function is easy and clearing attribute is easy also. But I don't know really how to restore the attributes of a function to its defaults. All I do is quit the kernel or close ...
3
votes
1answer
294 views

How to use Mathematica for traditional programming

I am new to the structure of Mathematica. I understand that in the notebooks, one enters the symbolic expressions and evaluates them. But I need to generate some simulated data and do that a few ...
34
votes
2answers
891 views

Why is the new PositionIndex horribly slow?

This issue has largely been mitigated in 10.0.1. New timings for the final test below are: ...
7
votes
1answer
207 views

Why can't a string be formed by head String?

Since everything is an expression in Mathematica, why must a string object be formed by "abc" but not by a String[abc] ...
2
votes
3answers
147 views

How to test for Indeterminate values?

I need something like this a = 101010/0; If[a == ComplexInfinity, True, False] But if I use ToString, I get what I want. ...
6
votes
1answer
155 views

Taking the derivative of a function with indexed variables

I have a number of functions that depend on a variable x. I am using a second, integer variable to index these functions, i.e. something like ...
1
vote
1answer
41 views

Strange behaviour of Set and Part when given a sequence

Consider this example: lis1 = {a, b, c}; lis1[[2]] = Sequence[e, f]; lis1 (*{a, e, f, c}*) lis1[[2]] (*e*) lis1[[2]] = Sequence[g, h]; lis1 (*{a, g, h, c}*) It ...
4
votes
1answer
92 views

How to define a formula in FormulaData?

I am looking for a way to manage frequently used formulas in my research, in a organized way in Mathematica. It appears to me that using FormulaData would be a ...
7
votes
6answers
440 views

How to build a list of functions

Having said that I'm no expert, I have some problems in generating a list of functions inside a loop. The functions in the list should depend on the elements of a parameters list, that are read in ...
1
vote
1answer
62 views

Why does WordData fail to find “PartsOfSpeech” when given a list of two words?

I have the following sample code. StringSplit["a test string", " "] Thread[WordData[%, "PartsOfSpeech"]] The output I get is: ...
4
votes
1answer
195 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?
22
votes
2answers
485 views

Why is Query so much slower than Part?

Time for another of these(1),(2) as yet another new-in-10 function appears to have poor performance compared to older alternatives. This time: Query appears to be ...
10
votes
0answers
287 views

Create a new infix operator [duplicate]

It is well known that the infix operator @@ is used as a short form of Apply. For example, both ...
6
votes
2answers
205 views

Why does Mathematica appear to change the head of certain expressions?

I don't know if the question trivial or not (if so I will delete it), but here is what I have: I know that x x (* x^2 *) Looking at the full form gives ...
14
votes
2answers
329 views

Can't get Append to append a record (association) to a dataset

The Documentation Center item, Computation with Structured Datasets, implies that Append has been extended in V10 to work with datasets. But not on my computer. (I ...
0
votes
1answer
117 views

Need help in understanding code [closed]

I am just beginning with Mathematica. I have received this code to study. I am not able to follow this particular section. I have tried looking it up on many forums, with no answer. Can you help? ...
3
votes
0answers
422 views

Is Wolfram Language suitable for building web applications? [closed]

My goal is to find a technology which will afford me to build web applications (e.g. simple social networking site) as quickly as possible (with as little code as possible). I was impressed by Stephen ...
4
votes
1answer
141 views

Multiple down-values with exactly the same lefthand side

I was working on an answer to this question, when I was sidetracked by what I bring up here. I wanted a function, which when given a string representing a binary number, would convert the string to a ...
2
votes
1answer
48 views

Is the use of Block to temporarily override definitions inherently unsafe? [duplicate]

This may have been discussed before, if so, please let me know. Consider the following example: x = 5 Dynamic[{Clock[], x}] This will always display the ...
1
vote
1answer
98 views

Why is Return not forcing an exit from my function? [duplicate]

Here is simplified version of my code that exhibits the behavior troubling me: ...