Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
0
votes
0answers
36 views
Correspondence between eigenvectors and eigenvalues [duplicate]
Let us say I have a matrix h (2x2). Now, I want to get the eigenvectors and eigenvalues of my matrix h:
...
4
votes
3answers
213 views
Separating positive and negative numbers into two arrays
$c$ is a vector with real numbers.I want to separate the positive ones and the negative ones into two vectors: $a$ and $b$.
I have the following problem:
When I do:
...
2
votes
2answers
215 views
Finding a best fit curve and plotting it [closed]
I have a list as shown below:
m01 = {{250, 0.083121}, {200, 0.0888446}, {150, 0.0992422}, {100, 0.121567}, {50, 0.186825}}
I'm new to Mathematica, and would like ...
0
votes
0answers
62 views
0
votes
1answer
61 views
Collecting roots of different equations and create a list
I solve two equations and have two solutions one by each equation. I want to create list of these roots. Could anyone please help me? Appreciate it.
m02R150 = FindRoot[P1 == 0, {E1, 0.07, 0.1}]
...
4
votes
2answers
122 views
Extracting data from a table under conditions
I have a very large table with two columns. Let's say the name of first column is E and the name of the second is P. How can I get the E values when P = 0.
3
votes
1answer
88 views
How can I get a single solution to a set of inequality constraints?
I have a set of constraints to which I require integer solutions. However, instead of needing all possible integer solutions (as obtained by using ...
1
vote
1answer
62 views
Calibrating Precision in calculations
As the title says, I encounter an irritating problem which has to do with the accuracy or the precision used in the calculations. To be more specific, I have the following code:
...
1
vote
0answers
101 views
Transferring a list from one notebook to another
I have Mathematica code split into two notebooks. The first part is supposed to run and output a list of numbers into a text file, using Export. The second part ...
6
votes
2answers
199 views
removing elements that are contained in other elements
For example, I have a list of lists:
l = {{a,b,c},{a,b,d},{d,e},{d},{a},{a,b},{f}};
And I want to remove all the lists that are contained in other lists:
...
6
votes
3answers
129 views
How to 'merge' a list like FromDigits, but with a mixture of numbers and symbols?
How do I go from {C,4,G,5,S,7} to C4G5S7
5
votes
1answer
153 views
Problem with creating a large list of tuples
This is a follow-up question from Sum of Multinomial Coefficients
I have thought about the meaning of the formula I mentioned and, with help, I implemented the following code:
...
9
votes
7answers
310 views
6
votes
2answers
163 views
Merging two Lists
I have two tables. One is given by
T1 = Table[{x, y, 0.}, {x, 0, V},{y, 0, V}]
and from a calculation I have the second, a list of points {x, y, z}
...
2
votes
4answers
233 views
Mapping over the last level of a list, or equivalent operations
I would like to style each element of my list using Style. But when I try
...
5
votes
1answer
267 views
Get the coordinates from ContourPlot and RegionPlot
How do I get the coordinates from a contour plot I've done in Mathematica? For example, I have a two-variable function f[x, y], for which I can make a contour plot:
...
13
votes
3answers
270 views
Quick multiple selections from a list
What is the fastest way to make multiple selections from a list? Compiled methods included.
For example, here are two methods for selecting a subset, compared:-
...
2
votes
1answer
153 views
How to solve equations self-consistently
I want to solve the following equation self-consistently. So,
H.u = e.u
{{1, d}, {d, 1}}.{u1, u2} = e.{u1, u2}
I guess an initial value for ...
-1
votes
1answer
70 views
How to separate a vector into two vectors, one having the first half of my original vector and the other having the second half
I have a set of n vectors with an even length. Let us make an easy example with 3 vectors of length=4:
...
1
vote
1answer
105 views
Creating an array eval [closed]
How can I create an one dimensional array (a vector) evaluating a function of two variables? I know how to do it with one variable:
Array[f, n, {a, b}] generates a ...
1
vote
3answers
106 views
Separate an array in two arrays, the even and odd terms being separated in these two arrays
How can I separate the odd terms in one array and the even terms in another array,i.e., go from
a={1,2,3,4}
to
aeven={2,4} ...
-2
votes
1answer
121 views
Non-regular grid data
I have issue with non-regulary spaced data. I have set of 3 numbers {x, y, z} in my list.
...
6
votes
1answer
227 views
Remove redundant brackets. Clean up lists
There are numerous examples whose end result is the removal of empty brackets "{}" and empty lists here, I still can't find an example of simply removing redundant brackets though.
(It's hard for ...
1
vote
3answers
161 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 ...
0
votes
1answer
60 views
How to get a number, but not a list, of the dimension of your array?
I need to use the dimension of a certain array, to use it as a bounder in a loop afterwards. The problem is that I get a list, when write :
...
3
votes
5answers
234 views
How to combine some elements of a list?
In order to simplify my expression, I face a list manipulation problem.
For example, given the input list
...
9
votes
1answer
163 views
Creating a number based on given conditions
In the grade 7 math curriculum here in Alberta we teach divisibility. I'm trying to write a program to create questions based on the idea of a student being given say, 4 digits, and then choosing ...
0
votes
1answer
133 views
Find Roots in Do loop
Task: Finding roots in loop
t = List[1, 2, 3, 4, 5]
fx[x_] := a*x^2 - 5
List[Do[Print[FindRoot[fx[k] == 1, {a, 1}]], {k, 0, 5}]]
Output: Currently the output is ...
5
votes
3answers
141 views
Elementwise join
I have two tensors of arbitrary but equal rank n (and equal dimensions): A and B, and I want to get a third tensor of rank n + ...
4
votes
5answers
119 views
Convert a list with three arguments {x0,x1, step} into an equidistant table?
How can I convert a list such as:
a = {1, 2, 0.1}
into sequence so that I can pass them into a function, e.g. I want to be able to do something like this
...
2
votes
3answers
140 views
Selecting subsets of a list containing a specific element
I'm trying to generate all the subsets of a set containing a specific element.
For example, for the set {1, 2, 3, 4}, with the specific element I want inside each subset being 4, the required answer ...
2
votes
1answer
94 views
7
votes
3answers
124 views
Multiply a list of matrices by a list of vectors
How does one multiply a list of matrices by a list of vectors, elementwise? For example, multiplying
...
3
votes
2answers
93 views
Sequence and boolean And
I'm trying to figure out if a calculation result it's a valid result. As it return a matrix, I need to test that every element it's a number, so I thought this could work...
...
6
votes
4answers
194 views
8
votes
4answers
271 views
Best way to modify values in a list of rules?
Recently I had to solve a problem similar to this:
Let's say I have a list of list of rules
...
11
votes
7answers
482 views
How to Set parts of indexed lists?
I would like to assign a list to an indexed variable and then change it using Part and Set like this:
...
7
votes
3answers
134 views
Given a list of lists, build a list in which lists with equal first and last elements are grouped together
I have a list of lists, and I'd like to build a new list, in which lists are in the same list if they have the same first and last element. Here's an example. Suppose I have
...
3
votes
1answer
102 views
How to make a simple tree yourself with defined distances for each generation?
I'm trying to make a function that generates a tree for spin spin analysis in spectroscopy. I though it would be pretty easy, but I'm totally stocked.
The tree should look something like this:
...
0
votes
1answer
98 views
Where do those nulls come from? [closed]
I have seen discussions of unwanted nulls in the output in the context of building lists with conditions on the elements, but that is not involved here. I would like to know where the nulls come from ...
4
votes
2answers
128 views
Partition a set into $k$ non-empty subsets
The Stirling number of the second kind is the number of ways to partition a set of $n$ objects into $k$ non-empty subsets. In Mathematica, this is implemented as ...
1
vote
2answers
163 views
Sum of Multinomial Coefficients
Basically I want to write a function to compute the following sum
$f(m,L):=\sum_{0\leq k_1,\cdots, k_n\leq m} \binom{m}{k_1,k_2,\cdots k_n}$ and $supp(k)=L \subseteq \left \{ 1,...,n \right \}$
I ...
3
votes
3answers
135 views
How to change a value within a list of lists?
I essentially have two questions, both are related.
1) How do I change a value within a list of lists (I provided a example problem)?
2) Why does my code not work?
I have a list which was created ...
8
votes
4answers
290 views
Passing large list by reference
I have the following problem: I would like to control evaluation of a variable that points to a list. For example, frequently in the code I have functions of the form that are supposed to work on ...
2
votes
1answer
63 views
Strange behaviour of variables in Table
I'm trying to work with some vectors and have run into a strange problem. An obvious way to define a difference of two vectors would be
dif[x_,y_] := x-y
I ...
3
votes
2answers
117 views
Listable compiled function using Map
I'm trying to minimize the computation time of problem which is too long to post. I use compilein order to gain some speed. To increase speed I would like to use ...
8
votes
5answers
336 views
Counting the population of integers
Suppose that myData is a list of sublists. Each sublist has a length of one or greater and contains any number of replicates of the integers 1, 2, 3, and 4. I ...
0
votes
3answers
148 views
Finding an index with certain conditions
EDIT: I need to find out an index i which depends on certain conditions and I'm not able to implement it. I have a list (time points) $t_i$ and two constants $a,c$ ...
0
votes
0answers
53 views
get while loop output into a list [duplicate]
I would like to get the output from this while loop and use it as a list so I can count the frequency of the various tuples..
...
0
votes
2answers
75 views
Converting a list of replacement rules into a list of real values [duplicate]
The following command outputs a list of replacement rules.
...
