Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
2
votes
2answers
54 views
Function returning Null along with other unexpected expressions
When I use some function, at the end along with the output I get some NULLs returned that I don't understand the reason for and are highly undesirable.
For example, when I define the reversal of list ...
2
votes
1answer
75 views
Generating a list of all factorizations
What is the best way to generate a list of all factorizations of some number $n$? I'm quite new to Mathematica so this might be obvious. I have been trying some basic stuff with ...
5
votes
3answers
97 views
Applying a function with the HoldAll attribute inside NestList
I'm trying to write an update function, which can be applied to a list and then to NestList it.
As the function has to manipulate the given variable I figured I ...
2
votes
4answers
133 views
How can I create a list of functions?
Can anyone tell me, how to create a list of functions? I've tried the following code, but it doesn't work.
...
1
vote
0answers
31 views
Indexing of Large System of Equations for Use in NDSolve
I currently have a list of ~150 DAE's (differential-algebraic equations) and I need to be able to work with using NDSolve. Fortunately I already have them ...
-5
votes
0answers
78 views
Extracting points data from a 3D curve surface?
I have a 3D data sets, and I have used it to create a 3D plot, but some of the data points are errors and need to be removed. How I can I remove the bad points from the plot?
...
8
votes
1answer
159 views
Efficient way to solve equal sums $x_1^k+x_2^k+\dots+x_5^k=y_1^k+y_2^k+\dots+y_5^k$ with Mathematica?
I need to solve the system of equations, call it $S_1$, in the integers
$$x_1x_2x_3x_4x_5 = y_1y_2y_3y_4y_5$$
$$x_1^k+x_2^k+\dots+x_5^k=y_1^k+y_2^k+\dots+y_5^k,\;\; k= 2,4,6$$
I used a very ...
5
votes
4answers
118 views
Tricky selection of elements based on their position
I need to make a list of some elements from a 4D array with dimensions 4x4x4x4. I need to select the elements based on their position in the following way: name an element e(x,y,z,w); I need all the ...
2
votes
1answer
59 views
Flat function with repeated sequence
There are functions like Join[ ] that accept a variable number of arguments. Join is a flat function, as the order of arguments ...
0
votes
2answers
84 views
Can you form a list with elements which are terms from an equation?
Is there a command that takes an equation as an input and creates an output with a list of terms in the original equation? Something like:
...
0
votes
0answers
76 views
Monitor the list for changes
I wrote a function to monitor the list of variable. What it does is if the variable in list change, the changed variable will be separated from others. check the function and output
...
0
votes
0answers
33 views
Generating partitions of a set with a specified size of the parts [duplicate]
I tried the following (inspired by the answer here)
myList = {a, b, c};
Needs["Combinatorica`"];
SetPartitions[myList]
and I got this answer,
...
-1
votes
0answers
59 views
Generate a list without braces? [closed]
Ultimately I want to plot a user-created function for many input parameters.
Plot[{P[1,k], P[2,k], P[3,k], P[4,k], P[5,k]}, {k, 0, 500}]
but I need to generalize ...
2
votes
2answers
91 views
How to select elements from a 4D Array?
I am very new to Mathematica (first time!) and I'm already having troubles with arrays. I basically have a 4D tensor, that is a matrix (call it M) which has for ...
0
votes
0answers
51 views
Problems with ListDensityPlot
I have the errors in one quantity $x$ in a List form as $(\Delta x,z)$, being $\Delta x$ the error and $z$ the value in which $x$ has the respective error. I want to make a density plot of the errors ...
14
votes
7answers
3k views
Mathematica: finding min/max in list
I have a list of coordinates like this one:
{{x1,y1},{x2,y2},{x3,y3},...,{xn,yn}}
I need to get the minimum and the maximum of all x-values and the minimum and ...
-2
votes
1answer
66 views
How do I operate on a set of ordered pairs? I want to square each inidividual element of an ordered pair and then add it
$$
[{{({-3 a, 3a}), ({-1a, a}}), {({-1a, a}), ({-1a, a}}})]
$$
I have a calculation that will give me a lot of these ordered pairs. What I wish to do next is square each element and add it to the ...
3
votes
2answers
152 views
How to replace Do loops by Inner
I need to replace Do loops by something else because it takes forever with big programs. I have been hinted towards Inner, but ...
7
votes
3answers
133 views
Making large tables easy to read with frozen headings and scrollbars [duplicate]
I would like to represent a table containing a large amount of information in such a way that I can (a) use scrollbars and (b) have table headings that don't scroll off the screen [just like the Free ...
25
votes
4answers
652 views
Partitioning with varying partition size
How can I partition a list into partitions whose sizes vary?
The length of the $k$'th partition is a function $f(k)$.
For example: if $l = \{1, 2, 3, 4, 5, 6\}$ and $f(k) = k$. Then
the partitioning ...
8
votes
3answers
130 views
How can I use the overhang argument to Partition to avoid using PadLeft and PadRight here?
Say I have a list of values v = {v1, v2, v3, ... }. I need to partition these values to perform operations with a sliding window (think ...
1
vote
3answers
109 views
Finding max, min, and closest root of two dimensional data
I have some data that is two dimensional (traditional (x, y) format) as so:
var = {{x1, y1}, {x2, y2}, {x3, y3}}
I would like to search through that large list ...
6
votes
1answer
88 views
How does `LongestCommonSubsequence` work?
When I recently came across this posting about LongestCommonSubsequence I was curious about how the function worked.
...
3
votes
2answers
117 views
Linear regression in a chosen range of points
Hi I'm absolutely newbie in Mathematica and have following problem:
My list looks like {{50, 0.75}, {51, 0.76}, ..., and I want to choose a range out of my ...
0
votes
0answers
60 views
2
votes
1answer
94 views
Create a table with inline conditions
I am trying to create a table with conditionals inline. For example, I'd like to create a 2 dimensional table like this:
...
7
votes
5answers
208 views
Multiplying two dimensional data by a constant
I have a list of lists of the form:
{{1, 2}, {2, 4}, {2, 8}}
But I want to multiply only the second dimension of that data by a constant. I know I could do this ...
4
votes
1answer
115 views
Sorting a matrix alphanumerically
Somewhat related to Sort matrix by columns and rows without changing them, but more general.
I'd like to sort a square matrix (a 3 by 3 in my case, but surely the general solution will treat any), ...
13
votes
5answers
255 views
Instruct a Table to only evaluate until a condition is fulfilled
I am looking for the way of building a Table of pairs of numbers in a fast way. My true table evaluates huge functions, and I see no way and reason to show those cumbersome expressions here. Let us ...
2
votes
2answers
120 views
How to populate a table using a rule replacement
I am trying to populate the rows and columns of a table by using a rule replacment.
To generate a table that looks like this
For example Sc would be row 1, column 1.
An example of a record looks ...
0
votes
2answers
83 views
Plotting array of vectors with conditions
Given data in the form
list={{{1,2},{3,4},{5,6}},{{7,8},{9,10},{11,12}},...}
a matrix where elements are 2-element vectors, what is a efficient way to plot this ...
0
votes
1answer
78 views
joining lists based on content
I have lists created by other processing steps, which are basically constituted by elements like this:
...
3
votes
3answers
68 views
Picking certain pairs according to a condition
I'm a Mathematica beginner and can't find out a solution to my problem. I have a list of pairs of numbers, for example something like this, but much longer: list={{2., 3.}, {3., 2.}, {5., 4.}, {4., ...
2
votes
1answer
82 views
Expand List Operation
On applying a multiplication and subtraction on a list, like so:
x = 2y - 4;
Where y is a list containing fractions of complex numbers generated from dynamic ...
5
votes
1answer
121 views
question about Inner
question1:
(code 1 something wrong, Why? and how to overcome this to achieve the next code's effect)
...
3
votes
4answers
121 views
Rearranging a set of numbers
I have this set of numbers, that is a range of prices (ie 6-10) and a quantity of products (5)
...
1
vote
1answer
59 views
0
votes
1answer
71 views
Breaking up data and finding independence
Suppose I have the list with elements (either 1 or 4 as the last digit)
as follows:
...
0
votes
3answers
82 views
Pass an empty list object into a function and dynamically generate its list elements
I have another question on passing a list which needs to be generated dynamically. (Sorry for posting two questions in one day...) I did some search and found a similar post here, but I think it was ...
6
votes
2answers
239 views
How to punch a hole in some 3D distribution of points
Suppose we have a long list of 3D Cartesian coordinates, defining a distribution of random points in 3D space. How could we remove all the points inside a sphere of radius ...
1
vote
1answer
97 views
Statistical analysis of data-list with recurring x-values
I have a list of data as follows with repeated x-values:
...
3
votes
1answer
75 views
0
votes
0answers
63 views
How can I solve this system of functional equations?
I would like to use Mathematica to find maps a, b, c, d, e, f such that
...
2
votes
0answers
88 views
Derivatives of list elements
Could someone explain the odd behavior of the Derivative function when drawing arguments from lists? We have,
...
2
votes
2answers
99 views
Importing several huge files with headers & footers
having here several files in ASCII format
http://ge.tt/91rv0Jf/v/0
I want to import, while removing headers and footers and then join the several lists.
...
0
votes
1answer
74 views
Using a loop to make a new list by taking elements from multiple lists [closed]
I have defined three lists and I need to be able to take elements from them periodically and put them in a new list. I know I need to use some form of a loop but I am at a loss. Any suggestions?
5
votes
4answers
222 views
Any rule of thumb for converting a simple mathematical expression into a pure function?
By simple mathematical expression I mean one with a few functions and few variables copied into MMA in a mechanical way from a math book.
For example this one, giving the distance between two points ...
0
votes
1answer
78 views
Dynamic List Building and Exporting [closed]
My ultimate goal is to have a text file that contains the following information in the following format exported to a text file:
...
1
vote
1answer
57 views
Splitting list of sums into a sum of lists
I want to split a list of sums into a sum of lists For example, I'd like to turn
{{x + y + z}, {x}, {y}, {z}}
into
...
5
votes
1answer
106 views
Is there an equivalent of “shiftdim” of MATLAB?
Recently I'm spending my time implementing some computer vision algorithms, which usually handle a large amount of data.
The problem I'm facing now is that I have to reform my video data to pass it ...
