38 questions linked to/from Flatten command: matrix as second argument
250 views

### How to remove extra levels in list [duplicate]

My question is how to turn a 4-level matrix (notice one extra level) A = {{{{1, 2, 3}, {4, 5, 6}}}, {{{7, 8, 9}, {10, 11, 12}}}}; into the following: ...
150 views

### How to understand the extensional usage of Flatten? [duplicate]

Recently, I have been reading Mathematica program that written by many advanced Mathematica user, like Mr.Wizard, J.M., Kuba,etc to improve my programming capacity In the On generalizing Partition[] (...
2k views

### Equating matrices (or higher order tensors) element-wise

Say I have two matrices (or, as in my case, higher order tensors) $A,B$, and I want to solve the equation $A=B$. To do so , I need a list of equations that equate entry-wise the elements of $A$ and $B$...
2k views

### Transpose uneven lists

Is there a quick method to transpose uneven lists without conditionals? With: Drop[Table[q, {10}], #] & /@ Range Thus the first list would have the ...
8k views

### Best way to create symmetric matrices

From time to time I need to generate symmetric matrices with relatively expensive cost of element evaluation. Most frequently these are Gram matrices where elements are $L_2$ dot products. Here are ...
3k views

### Ways to compute inner products of tensors

One way to evaluate the following sums is combining Table and Sum: $u_{abcd} = \sum_{e=1}^3 v_{aeb}w_{ced}$ $q_{ab} = \sum_{d,e=1}^3 v_{d e a}w_{deb}$ It will look like ...
882 views

### Prepend 0 to sublists

My question is similar to this one, but my goal is to prepend a single 0 the each sublist, not incrementally many 0's. The file I'm working is a CSV containing around 50K sublists of length 35. I've ...
1k views

### Using Transpose with a list as the second argument

I'm having difficulty understanding the Transpose function. I know what the transpose of a matrix is, not a problem, and I see that applying the ...
6k views

### How to get MATLAB data imported with the same dimensions?

I have some MATLAB image data with the following dimensions (output is from MATLAB): >> size(im) ans = 86 86 3 45 The data imports just fine ...
345 views

### Most efficient way to build block / banded SparseArray

I have a matrix that I generate with a procedure that looks like this: ...
448 views

### Part of the nested lists

Suppose I have a nested list where sublists have unequal length. How can I extract all values of the list at specific level ignoring errors if the value at that level doesn't exist. For example: <...
325 views

### Transpose two uneven lists [duplicate]

I am trying to plot two lists using the ListPlot command. I need to merge two lists. The two lists I have are: ...
301 views

### Riffle two matrices COLUMNWISE; where boh matices have the same number of rows

I need to "riffle" two matrices; COLUMNWISE. Say that we have: ...
3k views

### Flatten at a certain level

In an earlier question the brainteasing fourth syntax variant of Flatten was discussed. I see that with ...
847 views

### Translating MATLAB's cell2mat into Mathematica

How I can define a function in Mathematica such that it acts same as the cell2mat command in MATLAB? Example (in MATLAB): ...
1k views

### How to build a matrix from a set of vectors and other matrices using ArrayFlatten

I want to build a 6 by 3 matrix, from the following: one vector is 3 by 1, then a matrix, which is 3 by 2. These will go to the top 3 rows. Now the bottom 3 rows, I'll have 3 vectors each is 3 by 1. ...
1k views

### Understanding Transpose

It is very likely that it is my lack of math skills that is showing up here. However, I think Transpose is such an important function that I need to master it. So I ...
927 views

### Operations on elements of ragged lists

Suppose I have a list of lists with different lengths, sorted from longest to shortest ...
4k views

### Calculate mean and standard deviation from ImageHistogram

I am doing my PhD in Clinical Neuropsychology; I had someone helping me analyse images (.jpg pictures) in Mathematica, but it turns out this person made some really bad decisions, and well, now I have ...
380 views

### How to riffle matrices

I have four matrices ...
394 views

### Plotting how sunrise times change over the year

I created a somewhat lengthy Python code to show how the time of sunrise varies over a year, resulting in the following figure (daylight savings were disregarded): The dataset can be found here. The ...
485 views

### Applying the vec operator

How to apply the $\operatorname{vec}$ operator in Mathematica? For example, how can I transform a $2 \times 2$ matrix into a $1 \times 4$ matrix as follows?  \operatorname{vec}\left( \begin{...
185 views

### How to find all prime power factorizations of an integer

I want to put in $n$ and get the possible factorizations into prime powers. Let's say for 24 I want {{8,3}, {4,2,3}, {2,2,2,3}}. The algorithm for doing this on ...
254 views

### Inserting rows of one matrix into rows of another matrix sequentially

I have two matrices M1 and M2. Both have same number of columns but different number of rows. I want to make a new matrix M which should have 1st row form M1, second row form M2, third row form M1, ...
421 views

### How can I thread lists of different sizes?

What I need is the equivalent of Maple's zip(+, A, B, 0). Sure I can get it with: ...
83 views

### Decomposing a list into several two coordinate lists

How can the following list can be decomposed into separate two coordinate lists? list = {{1, {0}}, {2, {0}}, {3, {-2, 0, 2}}, {4, {-2, 0, 2}}, {5, {-2, 0, 2}}}; ...
94 views

### Adding the data of different tables

I have three tables of data say t1 = {{1, 2}, {2, 3}, {3, 4}}; t2 = {{1, 3}, {2, 3}, {3, 5}}; t3 = {{1, 3}, {2, 3}}; First I want to add ...
132 views

### Flatten a four dimensional array into a matrix

What is the simplest way to transform an array of the form ...