# Tagged Questions

Questions on the manipulation of List objects in Mathematica, and the functions used for these manipulations.

222 views

### Multiple level lists

Let there be a list, Sample={{{1, 2, 3}, {a, b, c}}, {{2, 3, 4}, {d, f, g}}} I want to go to individual sublists and do some operation on it.I tried a few things ...
176 views

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947 views

### A rotation-like transform on a matrix

Do not be confused with comments, those are for previous version of the question - Kuba Imagine I have a matrix of the form: ...
322 views

### How to group lists that own one common element?

I have produced a list of sub-lists by the following: ...
254 views

### Picking numbers within a list with an interval of 60

I have a list of integers from 1 - 400. I choose n random numbers with replacement from the list. Here is an example: ...
472 views

### Intersection for lists of numeric data

I know that Intersection is a pattern matching function and will not evaluate list elements to determine if two or more list have equal elements. So my question is, ...
2k views

### Mutual Information involving two matrix states

I basically retrieved the following technique of evaluating the mutual information involving two matrices from this site at http://bmia.bmt.tue.nl/People/BRomeny/Courses/8C080/default.htm The ...
568 views

### Gather list elements by index

The following list has some elements that are labeled. For example {1, 2} -> 1, {-1, 3} -> 3, etc: ...
248 views

### How can I use Pick to select items in one list when a value in a corresponding list is $\leq$ some value?

Imagine I have two lists: List1 = {0, 1, 0.6, 0.5, 1.2, 0.4}; List2 = {"a", "b", "c", "d", "e", "f"}; How can I use Pick to ...
172 views

### Create a Matrix out of two matrices

I have two matrices A = {{a1,a2},{b1,b2}} and B = {{x1,x2},{y1,y2}}. I would like to create out of these matrices a new matrix <...
46 views

### List elements and iterator name collision [duplicate]

Let there be two lists, exp = {{i, i}, {j, j}}; exp2 = {{r, r}, {o, o}}; and there are two Table commands to access them. Then, ...
395 views

### Using MapIndexed only at certain elements of a list

MapIndexed is a very handy built-in function. Suppose that I have the following list, called list: ...
631 views

### Span a function across several consecutive elements in a list

Suppose that I have a list called list. I would like to span an arbitrary function f across specified consecutive elements in <...
106 views

### Map and Scan ignore HoldFirst

I am trying to write a simple function that takes a list of data and outputs it to a file. I'd like the name of the file to be the same as the variable that holds the list. It seems that giving a ...
155 views

### Ways to access lists inside lists

I have gone through some reference material but I am not getting really good links that will help me grow understanding of ...
216 views

### Replacing all values in a table > $T$ [duplicate]

I want to generate a table of Euclidean distances from the points in a list to a given point, e.g.: ...
256 views

### How can I replace the general element of a geometric series with the sum of the series?

Consider the list mylist = {b(a/bc t)^r, a/b(b t)^r, a (c/d t)^r, ...} where a, b, c, t, etc., are real numbers between 0 and 1. I want to sum each term in the ...
262 views

### merge daily and hourly time series data

I have two lists of time series data. One of the lists is daily and is formatted like this; ...
314 views

### Multiplying expressions within a list of pure functions

Let's say I have a list of pure functions that are nice algebraic expressions: say l = {(#1 - 1)&, (#1^2 + #1)&, (#1^3 - 1)&} What's an easy way to ...
180 views

### Extracting counts of contiguous zeros and ones from a binary array

I'm a novice with Mathematica, but you guys have been very helpful to me in the past. I have a binary array [100, J repetitions] consisting of zeroes and ones. I'd like to extract a histogram of the ...
104 views

### How can I generate a generalized product to two lists in a special way? [duplicate]

Let's say I have two lists, and I'd like to generate a "cartesian product" from these two. Specifically Inputs: A = {{{1}}, {{2}}, {{1}, {2}}}; B = {8, 9}; ...
80 views

### Importing specific columns of a .txt file [duplicate]

I have text delimited file, with data in four columns. How to use ReadList to extract only the first and the fourth column.
182 views

### How to put a list of values on a single axis and add custom labels

I have a table in the following format: Apple 2 Pear 3 Banana 5 Orange 6.5 .... I would like to put the values on a single horizontal axis and add corresponding descriptive labels (apple, pear, ...
532 views

### Convert list of lists to cumulative join

I have this: list[1]={1,2,3}; list[2]={7,8,9}; list[3]={15,20,22}; I want this: ...
938 views

### Building a new table by repeating elements from another table

I have a small problem that I cannot solve. I have two tables, one with three elements: a = {0, L/c, 2L/c}; and the other with 9 elements, all 0: ...
1k views

### Removing pairs that meet a given criterion from a list [duplicate]

Let $(x_{min},x_{max})$ and $(y_{min},y_{max})$ represent lowerbound and upperbound acceptable values for some coordinate $c_i$. Setting $x_{min} = y_{min} = 1$ & $x_{max} = y_{max} = 9$, how ...
107 views

### Extracting only complete records from two data sets and combining them

I have two data sets: ...
203 views

### Combining the items with common available dates from two lists [duplicate]

I have two lists of data including dates such as data1 = {{{yy, mm, dd}, a}, ...} data2 = {{{yy, mm, dd}, A}, ...} There are some missing dates from each list, ...
254 views

### Bincounting a list

I'm a Mathematica novice here. I'm trying to execute the following code to add random 1's into a zero matrix, repeat this many times, and then bin/histogram the number of nearest neighbor 1s. Can ...
1k views

### Elegant and fast way to join all string sequences

I want to do what title says: {"a","b",1,2,3,4,"a",2,2,2,"edg","?"} => {"ab",1,2,3,4,"a",2,2,2,"edg?"} in the most elegant way. For example one replacement rule for ...
423 views

### Looking for an elegant way to construct this tensor-product-ish list

I would like to make the following matrix: ...
82 views

### How does PolarPlot render a nested list of functions?

I am getting unexpected plots from PolarPlot when I provide a list of functions that I generate using Table. I suspect the ...
984 views

### Removing not-a-number entries from an array of numbers

I have a list of {x, y, z} coordinates from a wavefront sensor I'm working with. However, not all of the imported points have actual values, but they still get ...
164 views

### list manipulation [duplicate]

I have a list like the following: {{1, 3}, {2, 5}, {3, 6}, {2, 4}} I want the final list to be like that : ...
125 views

### Non-canonical re-ordering of nested lists

I have some data in the form: ...
137 views

### Select rows of matrix that are higher than a given row

Imagine I have the following matrix: X={{0,0,0},{1,0,1},{1,1,1},{1,2,1},{3,3,3}}. I want to select the sublists that are greater or equal than this list ...
1k views

### How can I randomize order of elements in a list?

Is there a straightforward way to go from an ordered list like: ord = {a, b, c, d, e, f, g, h} to a disordered list like: ...
156 views

### Assigning Sequence to Part of a SparseArray (bug?)

Part ▪ You can make an assignment like t[[spec]]=value to modify any part or sequence of parts in an expression. ▪ If <...
617 views

### Find local maximum in 3D list

I have a set of data of the kind {{$x_i$, $y_i$, $z_i$}, ...} at randomly chosen points $x_i, y_i$. The $z_i$ are supposed to be a smooth function of the $x_i$ and $y_i$. Unfortunately they turn out ...
273 views

### Strange behavior of undocumented RawArray and ArrayObject expressions

I discovered several strange results and inconsistencies while trying to understand what undocumented RawArray and ArrayObject ...
514 views

### Measuring the area of non analytical regions in a plot [duplicate]

As the title says, I want to measure the area of different closed regions in a plot. Let me be more specific by giving a characteristic example. In the following figure, we observe that inside the ...
232 views

### Coarse-graining and/or sorting of a list of arbitrary triades {x,y,z} in the (x,y) plane [duplicate]

In general my question is related to an approach to make an interpolation of a data which is not on a regular mesh. Another aspect of this question has already been discussed after my question "...
725 views

### Sort+Union on a list

Probably this is too trivial question for this forum but for some reason I am not getting it on my Mathematica 7 so far. I have a list ...
464 views

### Performing Computations on Sets

I would like to find a permutation of $\quad S=\{\frac{1}{10}, \frac{1}{2}, \frac{4}{7}, \frac{3}{5}, \frac{2}{3} \}\quad$ that maximizes the sum of theses elements raised to unique powers: \$\;\{0,1,2,...
112 views

### How can I revise my program to avoid “No more memory available”? [duplicate]

I have a program for calculating a type of list. ...
144 views

### Forming product of function of prime factors

Given a list of numbers each containing 2 prime factors, I wish to make a list of the products of the logs of each factor. For example, given L = {4,6,9}, I would like to form P = {Log[2]*Log[2],Log[...
1k views

### Find elements of a list which are empty

Sorry for the most basic of questions. How would I find the positions of a list of elements which are empty, for example I have the list a = {1, 2, {}, {}, 3, 5}; ...
594 views

### Simpson's rule with ListConvolve or ListCorrelate

I have a function that's represented as a long list of values that I want to integrate. I can do it procedurally with Simpson's rule. ListConvolve generally runs faster then procedural code, so i ...