Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
1
vote
2answers
50 views
Counting a cardinality of a subset satisfying special property
Suppose that we have a set of 9 2-dimensional vectors $c$ by
m=3;
n=2;
c=Tuples[Range[m],n];
We want to define a subset $S$ of vectors in $c$ by the following:
...
2
votes
2answers
68 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
77 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 ...
1
vote
0answers
46 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
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
140 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.
...
-5
votes
0answers
80 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?
...
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 ...
8
votes
1answer
163 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
121 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 ...
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
34 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 ...
0
votes
0answers
52 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 ...
2
votes
2answers
92 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
77 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
...
1
vote
1answer
90 views
How do I operate on a set of ordered pairs? [closed]
I have a calculation that will give me a lot of ordered pairs. For each such pair in a list, I want to square the elements and add them together. Here is an example of the kind of list I have
...
3
votes
2answers
154 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 ...
0
votes
0answers
60 views
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 ...
1
vote
3answers
111 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 ...
7
votes
5answers
220 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 ...
0
votes
2answers
84 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)
...
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:
...
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 ...
1
vote
1answer
60 views
13
votes
5answers
262 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 ...
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 ...
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
...
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
2
votes
0answers
89 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
100 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.
...
5
votes
4answers
226 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 ...
1
vote
1answer
58 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 ...
5
votes
3answers
236 views
Replace “,” in a list with “.”
I have a list which consists of numbers which use comma (,) instead of dot (.) as their decimal point. I would like to replace the commas, but only those commas which are followed by more than five ...
1
vote
1answer
40 views
Partial row reduction of a matrix
I have an $m\times n$ matrix (presumably of full rank) with $m>n$, and I would like to row reduce it, but leave the last column unreduced; that is, I want to get output on the form
$\pmatrix{ 1 ...
0
votes
2answers
94 views
Convert *.txt file
I would like to Import and Convert a *.txt file which looks like:
https://docs.google.com/file/d/0Bw-308nJcF01Yl92RURCLUg4VzQ/edit?usp=sharing
and turn it into a Matrix which I can use to make ...
10
votes
4answers
329 views
Finding Local Minima / Maxima in Noisy Data
I'm trying to find local minima / maxima in noisy data, consisting of data values taken at certain time intervals. Ideally, the function should take a pair of lists (one containing time values and one ...
1
vote
3answers
93 views
How can I create a new tables out of a table and plot it
I have the following problem. I have a table, call it m, which is labelled by 3 indices (say i,j,k), each of them running from 1 up to 100.
I would like to be able to construct a new table which would ...
5
votes
1answer
105 views
nested use of Apply/Map/MapThread in pure functions
1. My main question
I have a function with two argument slots. I wan't to apply this function to 2 lists with different length's. I thought in this solution:
...
