# Tagged Questions

2 views

### Convert matrix rows into variables

Can anyone show me how to set all matrix rows to variables. For example, I have matrix w={{1,2,3},{3,2,1},{0,0,0}} and I need to set each matrix row to be separate variable that contains the row ...
28 views

### Find maxima and minima of data like {time,value}

I have a list of time and values of the charge and discharge of a capacitor, and i want to separate in two list of {time,value of charge} , {time, value of discharge} I know there is a lot of the ...
207 views

### Get 'new' list of data by manipulation 'old' list

Assume I have the the following list of data: valuesOld = {5, 10, 15, 20, 25, 35, 40, 45, 55, 65, 80}; I would like to construct the following list: ...
71 views

### Remove all “not equal” clauses from an expression

I am banging my head against the following question: how can I have Mathematica take cond = 2 a >= 3 b && 70 a >= 19 && 20 a != 13; and ...
78 views

### Creating and handling really large matrices [on hold]

I use Mathematica for a long-time to program physics simulation and I love Mathematicas programming style, but recently I am using fortran because it can do my calculations faster. I am doing some ...
225 views

### Faster Integer Approximation of pi

I'd like to speed up this calculation: First[Sort[Table[{k,Abs[Round[k/Pi]Pi - k]1.{k,1,100000}],#1[[2]]<#2[[2]] &]] The code above generates a list of ...
123 views

### getting at the right parts of a list

I have a way to solve my problem, but it seems like there should be something better. Also I realize that I probably don't have a good enough handle on how to get at parts of lists the way I need to. ...
516 views

### Join lists with nested list

Is there a way of smarter way of joining list of the form l1 = {a,{b,c}}; l2 = {d,{e,f}}; l3 = {g,{h,i}}; To obtain ...
50 views

### ListPlot and ListLinePlot, show nothing, how can I plot correctly? [closed]

I'm trying to plot a graphic using a list of pairs, i.e., {{x1,y1},...,{xn,yn}} but nothing appears in mathematica notebook. I used the following commands and list: Does anyone can help me please, ...
143 views

### Remove Successive Duplicate From A Large List (200k by 4 matrix)

I am interested in removing successive duplicate rows from a very large list (~200k rows by 4 columns) using Mathematica.The built-in 'DeleteDuplicates' seems to remove all duplicates, I am interested ...
41 views

### Convergence Problem using FindFit

I have the following input where there is a convergence problem in the FindFit as shown in the attached figure.The figure shows 2 plots: one of the real data and the other of the fitted line. Any ...
61 views

### list numbering problem

I have a list that is generated from a unparsed matrix, and another list that is generated by a parsed matrix. However, since the second one is parsed, the numbering of the elements in the list have ...
45 views

### parsing a list or vector

I have a table of elements that generate a list q[i_]=i; B=Table[q[i],{i,1,50}] I would like to parse the list meaning, take the first 10 elements, then take ...
36 views

### Not getting proper x-values in a ListPlot [closed]

I have a table of data points to be subtracted by another table of data points. I have succeeded in subtracting the y values of each data point successfully, but it is the x values of each data point ...
232 views

### Element-wise list operation on list of lists [closed]

Suppose a function F operates on list A: $$A=\{a_1, a_2,\cdots, a_n\}$$ I have a list of lists, B: $$B=\{A_1, A_2,\cdots,A_m\}$$ Is there a syntax to specify that F should operate on members of B, ...
45 views

### Read off entries of UndirectedEdge [closed]

Suppose I have an undirected edge e=UndirectedEdge[a,b]. How do I extract one of the entries a,b of e? I tried accessing e like a list, but that didn't work (...
156 views

### How to partition a list according to a value in the list

I have a list of the form $\{\{d_1,c_1\},\{d_2,c_2\},\ldots,\{d_n,c_n\}\}$. The values c_i take values between $1,\ldots,k$. I want to partition the data into $k$ lists according to the values $c_i$. ...
100 views

### Sorting out atom types in an XYZ file

I am trying to rewrite the output of "VertexCoordinates" such that instead of a hybrid list of atoms and coordinates that result from using the following input program, I want all coordinates of the ...
101 views

### Working with calculations that depend on the previous value in a list

I'm trying to make calculations on a list that depend on the previous value. In my case I'm doing event detection - detecting the point where a value rises above some threshold for the first time ...
121 views

### How to define even permutations correctly?

I define even permutations as following, but there may be some error. I use it in two different way and get different output. ...
154 views

### One to Many Lists Merge

I have two lists: ...
51 views

### Compare some lists, if elements are almost equal

I've got the solutions of three systems on two variables (a and b) that gives results sometimes almost equal. The three list are not of equal length! For example: ...
59 views

### How can I create a set (list) provide a kind of rule/algorithm?

Example: S = {r ∈ Q : r² < 2} Let S be the set of all rational numbers whose squares are less than 2. It follows that 1 ∈ S, 4/3 ∈ S, but 3/2 doesn't ∈ S because 9/4 ≥ 2. Thank you.
108 views

### How to multiply specific columns in a matrix of data?

So I need to make a plot of some ~2000 data points I have from a spreadsheet. I'm able to import the data just fine, it stores it like so sundat ...
61 views

### Remove values from list element, and add to other element

Basically what I need is to make a list of 400 elements, all have value 1. The next step is to create a function, that subtracts value (-1) from an element, and adds that to another element. So: ...
701 views

### Coalition Games

Suppose an election produces the following result: result = {{"a", 120}, {"b", 80}, {"c", 50}, {"d", 30}}; Letters are parties and numbers seats. To form a ...
91 views

### Random symmetric matrix

Suppose first that I want to generate a matrix whose elements are i.i.d. with distribution dist. This is easy: ...
204 views

### How to count number of observations/rows within each group

I have a huge unbalanced panel data. I want to count number of rows within each group. For example, I have the following data: ...
123 views

### Combining more than two lists by first column as index

Please bear with me. It might be easy but its been hard for me. I have say three lists: ...
42 views

### Column Operation - Subtract part of nested list from part of another nested list [duplicate]

I have two lists with x- and y-coordinates with different z-coordinates of the form {{x0, y0, z0_1}, {x1, y1, z1_1}, ..., {xn, yn, zn_1}} and ...
87 views

### Sublists of Random Permutations

What is an efficient way to create a list of (psudo)randomly chosen permutations? I'm trying to create a list like below: ...
54 views

### How to append to a list of lists elegantly [duplicate]

I have have list of lists and I would like to be able to append an element to the start of each list. I am sure there must be an elegant solution. EG: a and ...
45 views

### ListLinePlot of data imported from an Excel file [duplicate]

This is a continuation of another very similar question about how to plot structured data using ListLinePlot. Here is a sample data imported from an Excel file: ...
206 views

### Issue with very large lists in Mathematica

I have a need to work with very large arrays of data in Mathematica. The length of the list is not known upfront. The typical size is a few hundred thousands elements and could easily go beyond a ...
72 views

### How to efficiently select elements from a Hash?

How can I write an efficient version of the following selection statement: Keys[Select[hash, # < constant &]]; // AbsoluteTiming hash can be made from: ...
82 views

### Wrapping Interval Notation for Take

I'm trying to implement the solution to a math problem in Mathematica, but my code can't handle a particular boundary case. I think that I could implement a function that would do what I want it to, ...
99 views

### How to manipulate with external data?

I have a .txt file which contains a lot of triples (a, b, c) (one per row) which should be coefficients of my equation ax^2+bx+c=0. I want to include each triple in .nb file and solve each equation. ...
100 views

### How can I produce a list of solutions for a function which is updated with updated variables using for loop?

I need to loop over a set of equations, solving for X and adding the new X value to the old X value at each step. The output I need is a list ...
168 views

### Pick with nested list

I have a list of pairs of values. Some of those pairs are invalid based on another list. I would like to select only the valid pairs. ...
147 views

### Mapping a function over the parts of a deeply nested Array

I have two tensors: tensorS = Array[Subscript[s, #1, #2, #3, #4] &, {2, 16, 16, 19}]; tensorR = Array[Subscript[r, #1, #2, #3] &, {2, 16, 19}]; ...
385 views

### Is there a way to riffle more than two lists?

I thought Riffle would generalize such that Riffle[{a,b,c},{1,2,3},{x,y,z}] would return ...
82 views

### How to make functions from datasets

I have a csv that encodes the results of plugging certain parameters (say, A and B) into certain functions (say, ...
56 views

### Manipulating lists with uneven amounts of entries

So I have a list like so list={{a},{b,c},{d,e,f},{g,h}} and the basic logic I want is to be able to manipulate each of the nested lists individually. So If I ...
251 views

### Finding the coefficient of a certain power in a generating function

I want to compute $(t^1+\dots +t^5)(t^2+\dots+ t^6)(t^3+\dots +t^9)$ and find the coefficient of $t^{15}$ for example. $t$ is an indeterminate Now in Maple this is simply as ...
146 views

### Indirect transformation based on a list of data points

I have a set of data which describes the Intensity function $Int(q)$ as a function of $q$. The data list provided below provides the shape of $Int(q)$ versus $q$.How can I use this information to ...
119 views

### How to efficiently select element in a list of lists?

How can I write an efficient version of the following statement? Cases[list, {_, feature_} /; feature < constant]; // AbsoluteTiming List is of the form, list ...
155 views

### Breaking up combined data into several smaller data sets

I have one combined data with first number as the x-value and the remaining as different y-axis values (y1,y2,y3...). How do I break this combined list, data= (x,y1,y2,y3...) into smaller lists, such ...
204 views

### Is there a bug in the Part function of Mathematica 10?

I am using Mathematica 10 now. I typed code below {{1, 2}, {2, 4}, {3, 6}, {4, 8}}[[;; , 1]][[1]] and this gives result 1 ...