Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.
7
votes
1answer
111 views
Transformation rule on a list of non-negative integers
I am trying to create a transformation rule that takes a list of non-negative integer values of any length, finds a non-zero entry in the list, adds 1 to all preceding numbers, subtracts 1 from the ...
7
votes
3answers
235 views
Find all the last weekends in a year
In order to obtain the weekends of a year you'd use something like this:
...
7
votes
3answers
308 views
Analytically finding critical values in a hysteresis curve made with ListPlot
Let me start with a super basic explanation of what I'm trying to do, and I will follow with a more detailed discussion afterwards.
From data in the form shown below (a ...
7
votes
3answers
205 views
Restricted accumulation of values
Please consider the following list data. I was trying to accumulate data until the result turns positive the first time and ...
7
votes
1answer
251 views
Very fast way to do a coordinate frame transform
I need a function that rotates and translates a huge amount of line segments.
For example, I have a set of line segments in the form {{x0,y0,z0},{x1,y1,z1}}
...
7
votes
1answer
147 views
Built in way to de-list singletons?
Is there a built in method to de-list singleton expressions, like this rule-based solution:
expr_ :> If[Length[expr] == 1, First@expr, expr]
In data ...
7
votes
3answers
134 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 ...
6
votes
7answers
285 views
Adding elements to a collection of lists
I would like to add element a at the start of a series of lists.
For example I have a collection of lists called
...
6
votes
4answers
338 views
Convert head Times to List
I can convert an expression with the head of Times,for example, 12*12.5*13*13.5*14*14.5 to {12, 12.5, 13, 13.5, 14, 14.5} by ...
6
votes
5answers
312 views
remove -1 values from a list
I would like to turn a list which looks like this one:
{{-1, -1, -1}, {-1, 2, 3}, {-1, -1, 2}, {2, 3, 4}}
into one which looks like that one:
...
6
votes
6answers
273 views
How can I merge two lists in a special way?
It's been over a year since I've used Mathematica, and I'm having a total brain fart on a home project. I'd like to take an existing list of lists, say,
...
6
votes
6answers
708 views
extract values from replacement list
Solve returns a list of replacement rules
In: Solve[x + y == 3 && x - y == 6, {x, y}]
Out: {{x -> 9/2, y -> -(3/2)}}
I am only interested in the ...
6
votes
3answers
293 views
Sum over binary digits of integer
This might seem like a simple enough question but Mathematica seems to simplify inadequately here:
How would you sum over the digits of an arbitrary binary number?
I already tried this:
...
6
votes
3answers
154 views
List has a date and amount, I need to create a cumulative amount by date
I have a list which has a date and a amount, I need to create a list that has the cummulative total with the date.
I have the following result:
...
6
votes
4answers
213 views
How to apply a function to a list of tuples
trialList = {{0, 24.701}, {1, 24.69}, {2, 24.733}};
f[x_] := x + 1;
I would like to apply the function f to only the second ...
6
votes
5answers
249 views
Computing the equivalence classes of the symmetric transitive closure of a relation
I have a list of pairs, for example:
...
6
votes
2answers
193 views
Map a function over the columns of an M x N array
I have a $N \times M$ list of lists, or rather, a list of records and I want to map a function over its columns (e.g. find the mean temperature, age, etc.). Map ...
6
votes
2answers
241 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 ...
6
votes
4answers
404 views
Alternatives to While Loops?
I am using Mathematica to run a probabilistic simulation. Essentially, I have a list of members of a population (they only have one, numerical, attribute, so it's just implemented as a list of ...
6
votes
3answers
347 views
Generating a non-convex polyhedron from a list of vertex coordinates
I want to include a figure in a paper I am writing on Combinatorial Geometry which features a non-convex polyhedron given by the following vertices,
EDIT: I was unaware that Mathematica could convert ...
6
votes
3answers
227 views
How to take part (and then sum over) of specific level of an array?
Specifically, I want to take some elements of the lowest level of an array, and then sum over these elements while holding the higher level.
Sorry for my vague expression, maybe an example would make ...
6
votes
4answers
194 views
6
votes
3answers
200 views
Filtering elements from a list
Suppose that I have a list
{{{2, 1}, {4, 3}, {2, 4}}, {{2, 1}, {4, 3}, {3, 1}},
{{2, 1}, {2, 4}, {3, 1}}, {{4, 3}, {2, 4}, {1, 2}}}
I want to make a new list ...
6
votes
4answers
122 views
Is there a good way to map a function over a list to lists exclusively of a certain depth?
Let's say I have some ragged list. If some elements have some depth $n$, then is there a way I can map a function to only those elements?
I.e., for some list foo,
...
6
votes
1answer
233 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 ...
6
votes
4answers
165 views
How to sum over duplicates?
I have a list of the form:
{{1, 0, 1}, {2, 1, 2}, {1, 0, 3}, {2, 4, 2}, {2, 1, -1}, {1, 0 ,0}}
that I would like to sort such that I calculate the sum over the ...
6
votes
3answers
273 views
Specifying string patterns in DeleteCases
It seems that DeleteCases is not compatible with string patterns, at least directly (see, for example, this question). Is this true? If so, why is this the case? ...
6
votes
3answers
243 views
print the name of the variable in a list without evaluation
a := az + 1
b := bz + 5
list := {a, b}
I'd like mathematica to print
a = az + 1
b = bz + 5
so basically it needs to first ...
6
votes
2answers
165 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}
...
6
votes
3answers
122 views
Importing and manipulating strings - time data
I have a list of time durations, which are strings of the form: "hh:mm:ss". Here's a sample for you to play with:
...
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
6
votes
2answers
190 views
6
votes
2answers
120 views
DateList Segmentation of data
I've been trying to separate large segments of DateList formatted data (years worth at a time) into individual days using the Split function.
The data has the form: ...
6
votes
3answers
415 views
Subsets of a list
Consider the following demand of products for the next four months.
data={1,20,3,40};
I could produce the whole demand in the first months, leading to the ...
6
votes
2answers
181 views
Operate on several lists to create one list
How do you put corresponding values from different lists together according to some operation?
E.g. I have three lists giving the velocity in the x, y and z direction respectively. I'd like create ...
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
2answers
420 views
Finding all partitions of a set
I'm looking for straightforward way to find all the partitions of a set.
IntegerPartitions seems to provide a useful start. But then things get a bit complicated.
...
6
votes
3answers
191 views
6
votes
1answer
76 views
Position with Except returns first item {0} and last item {}. Why?
Here is a simple list:
l={1, 0, 2, 1, 0, 1, 0, 1, 2, 0, 2, 0, 1, 0, 1, 0, 0}
To get the position of non-zero elements I use ...
6
votes
1answer
95 views
Implementing Remainder Tree
I want to implement Remainder Tree based on this. With the answers on SE I've come up with:
...
6
votes
1answer
194 views
How to compile Map and MapAt
I have a long list (say, million of elements, like this one:
{{{1.0, 2.0}, 3}, {{4.0, 5.0}, 6},...}
I would like to compile a function ...
6
votes
2answers
324 views
Building matrices by attaching vectors (columns) and matrices
Having the need to attach a column to a matrix or to join matrices to make longer rows is an operation that I use very frequently and I find the Join function ideal ...
6
votes
3answers
229 views
How to Gather a list with some elements considered unique
I have a list of the form:
list={{0,...},{1,...},{1,...},{0,...},{3,...},{3,...},{0,...},{0,...},{5,...},{5,...},{5,...},{0,...},{5,...},{0,...},...}
So when we ...
6
votes
2answers
139 views
Select elements of list within a date range
I have a list which consists of elements each of which has a date in DateList format, a number and a flag (Y/N). e.g.
...
6
votes
1answer
136 views
ReplaceAll inside an Iterator
I'd like to apply a set of rules to an expression defining the iterators of the table, like this:
...
6
votes
5answers
211 views
Handling holidays in financial time series
I have two lists: list1and list2, which are financial time series with only 2 variables—date and price. The problem is: these ...
6
votes
1answer
202 views
Finding all length-n words on an alphabet that have a specified number of each letter
For example, I might want to generate all length n=6 words on the alphabet {A, B, C} that have one ...
6
votes
1answer
128 views
Elementwise, compilable min function
I am trying to implement efficiently a transfer-matrix like algorithm. On each iteration, I have two vectors $x=\{x_1,\dots,x_n\}$, $y=\{y_1,\dots,y_n\}$ with real numbers and I need to compute the ...
6
votes
2answers
204 views
Merging different size, different order table
I'm a beginner in Mathematica, so this may be a simple request. I have generated some columns of names and data. I want to merge them into a single list of names, with a column for each attribute.
...
6
votes
2answers
202 views
How to choose variables from a list for a function and then use the solution in a subsequent function?
I am trying to calculate heating degree days and cooling degree days and output that information to a table. I am using mathematica's curated data to do this. In text this is what I would like to ...
