Linked Questions

0
votes
1answer
4k views

Loops and subroutines [duplicate]

Possible Duplicate: Alternatives to procedural loops and iterating over lists in Mathematica I am new to Mathematica and not familiar with functional programming. In particular, I have no idea on ...
0
votes
2answers
623 views

Seeking faster method than using Table and If together [duplicate]

See the example below. Is there any way to make this execute much faster and still get the same output ? I have read Conditionals slower than operators? but it didn't really help me as I can't seem to ...
1
vote
1answer
728 views

For loops in Mathematica [duplicate]

I'm actually the first time using loops in Mathematica. For example, I have: For[i = 1, i <= n, i++, For[j = 1, j <= n, j++, ....] How it is possible now ...
1
vote
1answer
253 views

How should I go about writing more functional and list based code? [duplicate]

I've heard that Mathematica is usually faster when the code is list-based and/or uses a functional paradigm. I'm still working on getting the hang of this; there are a lot of ...
6
votes
0answers
158 views

What are some general strategies to avoid using For loops? [duplicate]

Possible Duplicate: Iterating over lists in Mathematica While there are some cases where a For loop might be reasonable, it's a general mantra – one I ...
2
votes
0answers
117 views

Want explanation of when different looping constructs are appropriate [duplicate]

For example when would you use a Do loop over a For loop? For which tasks would you use Map, ...
0
votes
0answers
57 views

What techniques have you employed to avoid loop in Mathematica? [duplicate]

It appears to me that loop in mathematica is very slow (compared with matlab). Since many people still use mathematica to finish their work, there must be some techniques to bypass this problem. ...
472
votes
37answers
108k views

What are the most common pitfalls awaiting new users?

As you may already know, Mathematica is a wonderful piece of software. However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from ...
553
votes
19answers
140k views

Where can I find examples of good Mathematica programming practice?

I consider myself a pretty good Mathematica programmer, but I'm always looking out for ways to either improve my way of doing things in Mathematica, or to see if there's something nifty that I haven't ...
39
votes
12answers
3k views

Map a function across a list conditionally

It seems that this is a really basic question, and I feel that the answer should be obvious to me. However, I am not seeing. Can you please help me? Thanks. Suppose I have a list of data ...
94
votes
4answers
16k views

Why should I avoid the For loop in Mathematica?

Some people advise against the use of For loops in Mathematica. Why? Should I heed this advice? What is wrong with For? What ...
59
votes
5answers
6k views

Are there any cases when For[] loops are reasonable?

To my mind the only reason for the existence of For[] loops in Mathematica is to allow new users with some experience in procedural programming languages to write ...
18
votes
7answers
5k views

How do I check if any element in a list is positive?

As a simple example of what I would like to do, suppose I have a list a of all real numbers. I would like to perform a simple check to see if some element of ...
51
votes
2answers
6k views

Scan vs. Map vs. Apply

I cannot understand the difference between Apply, Scan, and Map. I have tried to play with ...
9
votes
8answers
2k views

Finding the midpoints of an ordered list of numbers

Suppose that I have an ordered list of numbers. The numbers in the list may be evenly spaced, but they may not be. Here are two examples, list1 and ...
11
votes
4answers
10k views

Removing all values from a list that satisfy a given condition

Suppose I have a list, list = Table[{n}, {n, 1, 5}] (* list = {{1},{2},{3},{4},{5}} *) and I want to remove all values from this list that are greater than 3, so ...
19
votes
2answers
999 views

Shorthand for map at level 2

I love the shorthand /@. It is amazing for readability (and laziness when typing). However, right now I find that I need Map at level 2, i.e. ...
8
votes
2answers
9k views

Creating custom functions with multiple arguments

I am hoping that this isn't a stupid question so feel free to vote it for closure. Google failed somehow. I want to define a custom function (more complicated than the usual ...
9
votes
4answers
3k views

Implementing Picard's Iteration for solving ODEs

Picard's Iteration is a way of solving the IVP $$y'(x)=f(x,y(x)), \quad y(x_0)=y_0 $$ It consists of defining the following sequence of functions recursively: $$y_0(x):=y_0 \\ y_{n}(x):=y_0+\int_{...
2
votes
6answers
3k views

Selecting elements from a list one by one

I have an list: l = {{4,5},{7,8},{9,5},{3,2},{1,2},{13,12}}. I want to take the elements in the list in the sequential order. For example the first element in ...
13
votes
4answers
508 views

The gap between MapAt and ReplacePart for 2D data tables with headers

Consider a relational table derived from survey data, where each column ("001-01" ...) represents a responder and each row (...
7
votes
5answers
929 views

What is primary, function computation or function application?

What is the order of computations here? g[x_]:=x^2; f[x_]:=Sqrt[g[x]]; Map[f, Range[100]] Does this code first gets $f(x)=x$ and then gives its values or for ...
11
votes
5answers
2k views

Relational joining of tables

A common thing to want to do with data is to combine it (at least I thought this was a common thing). In SQL there is the idea of table joins "select id,v1,v2 from A,B where A.id=B.id" kind of thing. ...
5
votes
3answers
306 views

First evaluation fails

I am fairly new to Mathematica (version 7), so please bear with me... I have duplicated, in Mathematica, a program that I originally wrote in C (it generates OEIS sequence A191837). The problem is ...
1
vote
3answers
6k views

Loop through a list and select elements

I am new to Mathematica and I have no idea how to make a basic for loop work. I want to loop through the elements of a list: Range[45, 200]. I want to select the ...
8
votes
3answers
703 views

Rewriting For loop to FoldList or similar

In CrossValidated, the answer to a question on prediction of number of viewers of Gangnam Style is given in R. I have mapped the answer directly to Mathematica: ...
5
votes
3answers
881 views

Is Table the only functional way to construct nested loops in Mathematica?

Suppose you have a cubic box containing identical particles and you want to compute the distances between each particle and every other particle in the box without double-counting (i.e., if you've ...
5
votes
3answers
1k views

How to speed up a process

I am wondering how to speed up the following code: Currently it takes more than two sec to be processed. ...
0
votes
3answers
1k views

In nested For-loops, I want the second For-loop to be evaluated only once in each cyle

I want to print A[0, 0, 1], A[0, 0, 2], A[1, 1, 1], A[1, 1, 2], A[2, 2, 1], A[2, 2, 2] using the following code. ...
2
votes
4answers
4k views

How to export data from For loop in text file?

I'm new in Mathematica and I am trying to write numbers from 1 to 10 in txt file. But "Null" is everything that is written in my file. The code is: ...

15 30 50 per page
1
2 3 4 5