# Tagged Questions

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

213 views

### Flip sign of one variable in list

I have this list of x, y-pairs l={{x1, y1}, {x2, y2}, ...}. Now I need to flip the sign of the y values only before plotting. What is the easiest way to do this ...
125 views

### Creating a Random list with constraints

I need something similar to the List below, but not totally random and values within each individual column and row remaining the same: ...
78 views

### List of first elements

I have a list whose elements are (symbol or list) and I would like to replace the inner lists by their first elements. I do this ...
459 views

### Easiest way to extract the coefficient of a polynomial

For a term in a polynomial, say 387 a1^4 a2^3 x^3 y^7 z^100 w^364 what is the most efficient way to extract the coefficient of this term, i.e. ...
68 views

### How to delete list items that contain a non-numeric Part

A sample of the list looks like this: ...
284 views

### Creating new List by comparing 2 lists elements

Suppose I have two Lists (Not equal length). Both contain random numbers between 0 to 5000 (or another max limit): ...
53 views

### How do I add the nth element for every line in a text file?

Suppose I have a text file, in this format: ...
86 views

### Fitting a Gaussian model to specific section of my list?

I'm analysing some Decay sepctrums for a Nuclear Physics project. I need to fit a gaussian model to a specific X-Ray peak to determine the centroid so I can get a good channel-energy calibration. ...
159 views

### How to expand a MxM matrix with replicates of itself and drop some of the rows and cols periodically?

How can I expand a 2d-matrix with dimensions x,x (e.g. mat = {{ 1, 2 }, { 3, 4 }}) with replicates of mat into ...
52 views

### Returning maxima of multiple sets

I am trying to prove a conjecture which involves the SetParitions[n] function (which requires the Combinatorica package). This function returns a list of all the set partitions of n. I'd like to take ...
170 views

Consider: ...
76 views

### Mysterious Riffle::rspec warning

I have part of a code that looks like this: ...
111 views

### Filtering and summing sublists with Cases

I've declared a list: list = {{1, 2}, {2}, {3, 4, 1}, {5, 4}, {3, 3}, {a, b, c}, {e, f}, {g}, {}, {Sin[a], Cos[b]}}; now I've made an rule which add 2 pairs ...
41 views

### How to delete lines containing specific values from a matrix? [closed]

I am doing some numerical computations and a few iterations return values that are obviously incorrect (some numerical integration problem, I suppose.). I have managed to set these values to zero but ...
25 views

### Matching list entries by two values, adding the third [duplicate]

I have data in form of: data={{1,1,3},{1,1,6},{2,1,7},{2,2,4},{2,1,1}}; I want to match the entries with the same first two elements and add the third element in ...
45 views

### Select and use only one solution in a list solutions [closed]

I would like to use and plot only one of the two solutions of a quadratic equation. In particular this is my equation ...
62 views

### How to output the entries of two lists as equal without evaluation? [closed]

Question So, for example, I have the code here: ...
123 views

### Alternative for AppendTo [duplicate]

as I'm well aware, using AppendTo for large lists isn't recommended as the function gets progressively slower with each appending done. Lots of suggestions talk ...
97 views

### Automatically generate and manipulate variables in Mathematica

First line is just loading data from a txt.file, so that i get two lists {f1,f2,f3,..},{laser1,laser2,laser3,..}. How can I do the same thing as above in just one line? i.e. I have a list of laser ...
42 views

### Applying slots, one after another for a list [closed]

For this function: Fun[x_] := 3 x^3 + 4 x^2 - 2 x - 1 I apply Map: D[Fun[x], {x, #}] & /@ Range@3 and I get this ...
84 views

### DeleteDuplicates [closed]

After having applied "DeleteDuplicates" to a list of data (15000 rows per 3 columns), when I try to interpolate that list of data it gives me back again: "There are duplicated abscissa points in.." ...
55 views

### How To extract data to plot it from a log file

i want to extract out the data (number) from 'geometry step' and 'total energy' in form of list to PlotList[] it. this is the Log file data log Abstract the Total ...
144 views

### ListPlot with colors

Let's create some sample data n = 100; d00 = Table[{RandomReal[{-1, 1}], RandomReal[{-4, 4}], RandomReal[{-1, 1}]}, {i, 1, n}]; Now I want the following: create ...
55 views

### Export list entries under a certain condition without using loops

I have a big list that contains many 3D- chains (set of points) and for each of them a polynomial. So the structure of my list is for example ...
62 views

### Distinguish hashtag # operator when using multiple functions [duplicate]

I would like to do this list = Append[list[[#]],Map[list2[[1, #]] & , list[[#, 4]], {2}]] & /@ Range[Length[list]]; But I would like to substitute ...
46 views

### TexForm List with Rule

I'm having some difficulty TexForming a list. The output is not what I want. The following is a minimum working example. I've tried every combination of Flatten, ArrayReshape, and Partition to no ...
74 views

### Export many lists without using loops

I have a Mathematica function that creates a RandomWalk chain of length l, by generating random points on the unit sphere and ...
43 views

### Setting the value of a list item

I want to set the value of an item in a list. The code that does this has to work regardless of the depth to the list. For instance set the value of r[[1,1,1,....,1,1]] to 9. Lets say the list called ...
73 views

### Automatic process to replace missing values, coming from a second matrix

I have a large starting matrix with missing values in different columns. I want to replace this missing data as follow. First I have to check the group (last column in starting matrix) and go to a ...
60 views

### Discard Elements of list with given criteria

I have the following list: ...
91 views

### Count pairs from a List

I have a list of numbers: ...
77 views

### Pareto optimal fronts using internal function?

Reading this question: How do I estimate the Pareto front in my multiobjective optimization problem? I found @Daniel Lichtbau's interesting answer. Yet I don't know how such an "internal function" ...
179 views

### Is there a way to PrependTo or AppendTo while flattening the result in the same step?

arr = {1, 2, 3}; PrependTo[arr, {a, b}] (* {{a, b}, 1, 2, 3} *) But, I want (* {a, b, 1, 2, 3} *) I know I can use ...
141 views

### how to apply Alternatives command to delete cases from a list?

I have two lists let say listF = {{7, 2}, {2, 6}, {8, 1}, {1, 7}, {11, 8}, {6, 11}}; and ...
73 views

### Duplicate rows with multiple entries

I have a huge dataset, which looks similar to this: ...
107 views

### Find the minimum element of a row of a matrix and its column index for each row

I am trying to find the minimum value of a row of a matrix and its corresponding column. Please run the code below. OptV is the matrix that I would like to create which must give the output of the ...
351 views

### Find duplicates in list of InfiniteLine

MMA 10 introduced a new function, which can be very convenient: InfiniteLine. Of course, two infinite lines can be described by different arguments: for example <...
63 views

### Matching a Table and a List and building a new Table

I have a Table which includes {Numbers, Probabilities}. For example A= {{1,0.5},{2,0.25}, {3,0.1},{4,0.9}……{100,0.1}}. Put attention that the numbers are 1,2….100 in order. I have a List of random ...
240 views

### How do I encode this replacement rule?

I'm pulling a 5x5 array from a larger array. The small sub-array (call it S) can contain any combination of the symbols A, B or 0. What I'd like to do is: if the array contains any matching pairs ...
81 views

### What's the easiest way to find the closest point in a list of pairs?

I frequently end up in this situation. I have a solution, but I suspect it's the dumbest way of doing it. Frequently, I'll have a list of pairs, for example: ...
46 views

### NRoots Results: From Equations to List of Root Values [closed]

When I use Roots/NRoots, I get a disjunction of conditions as result. The conditions are normally of the type x == value How can I convert this to the list of root values?
76 views

### Creating a custom ListPlot of consecutive points

Here comes some sample data ...
304 views

### How do I split a list of numbers to monotonic sequences?

Suppose I have: list = {1, 2, 4, 5, 7, 11, 8, 7, 3, 1, -3, -2, 6, 7, 80} And I want to split it to: ...
76 views

### Untangling a tangly block of If statements

This is a followup to my previous question: How to simplify block of multiple repetitive If statements? I have another block of If statements, somewhat like the other one I need help simplifying (...
107 views

### Extract every nth character from a string

I'm trying to extract every 21st character from this text, s (given below), to create new strings of all 1st characters, 2nd characters, etc. I have already separated the long string into substrings ...
180 views

### Drop in nested tables?

I want to drop a specified number of elements from a 'table ...
454 views

### How to simplify block of multiple repetitive If statements?

I'm building a boardgame...game in Mathematica. I have the board state represented as a matrix. It's a two player game, and each player (let's call them A & B) only has one type of piece or '...
140 views

### Find the length of the intersection of two lists including duplicates

I have 2 Lists. The first one includes all the numbers from 1 to 10. listA={1,2,3,4,5,6,7,8,9,10} The second includes ...