# All Questions

62,797 questions
Filter by
Sorted by
Tagged with
0answers
39 views

### How to solve this DE to get a matrix?

I have this DE $g^{m \bar{n}} g^{r\bar{p}} \partial_t {g}_{m r} \partial_t {g}_{\bar{n}\bar{p}} = X_{i\bar{j}}~ \partial_t{f}^i (t) ~ \partial_t{f}^\bar{j} (t) ~~~ ~~~~~~~~~~~~(*)$ Where ...
1answer
66 views

### How can I solve this equation for the exponent n?

How can I solve: $$(a^{n-5/2}-b^{n-5/2})=c$$ for $n$? $a$, $b$ and $c$ are known constant. It seems that Solve cannot solve it and ...
3answers
589 views

### WordCloud: do not eliminate duplicates

By default, WordCloud removes duplicates (or rather counts the number of times they occur, and uses that as the weight). Is there a way to turn this feature off, ...
4answers
135 views

### How to count the overlapped disks in a picture?

I have several picture containing many small circles. I can manually count the circles in these pictures but it will be time-consuming and make me tired. How can I use mathematica to do this job? I ...
1answer
43 views

### How to condition arguments of a pure function?

I would like to exclude the point {x=0,y=0} in the function definition ...
0answers
58 views

### Derivative of eigenvalues

I work with 4x4 Hermitian matrices (r). I want to calculate a derivative of a function f[t,r] (ff[t_,r_]=1/2*D[f[t,r],t]), where the function f depends on the absolute value of the eigenvalues of r. ...
3answers
103 views

### Map function over two lists

How to map a function over two lists, first one and than the other? For example, assuming I have two lists {a,b,c} and {d,e,f}: ...
0answers
31 views

### How to define a function in an implicit form

Know the 2-variables function $F(x,y)$. How can I define the function $x\to f(x)$ s.t. $F(x,f(x))=0$?
3answers
95 views

### Sparse matrix processing: flip sign of top-left entries of the matrix

I have a 12k X 12k sparse array (~1% density) and I need to: take the square root of all the elements flip the sign of all the elements in the top-left half of the matrix For example, say that the ...
1answer
36 views

0answers
37 views

### Improve speed of NIntegrate for functions which are sums of complex exponentials

I need to improve the efficiency for numerically evaluating a matrix element, which uses NIntegrate of the several functions (which are all sums of complex exponentials). Creating the functions from ...
2answers
109 views

### Group symbols by a given partition of the occuring symbols

I have following expression $$-3 b_{\sigma _d}-3 b_{\sigma _v}-b-b_2+2 j-2 j_2-2 j_3+2 j_6+12$$ Mathematica input ...
0answers
63 views

### Repeated string pattern: difference between the FrontEnd and WolframScript?

This code works fine in a string based interface like WolframScript or Mathematica Kernel. Run this through a string based interface ...
0answers
43 views

### Discrete inverse Laplace transform

I'm trying to find a method for obtaining the inverse Laplace transform of a series of discrete data points. I have tried deriving an analytical function from the data and then using that function ...
1answer
34 views

### Coefficient Array from total derivative of expression

I have an expression $$\dot{r}\dot{\eta}+r^{2}\dot{\theta}\dot{\xi}=0$$ where $\eta$ and $\xi$ are both functions of $r,\theta$. In MM I wrote this as ...
1answer
78 views

### Can we compile this function/distribution?

I would like to compile this function to make it faster: ...
1answer
77 views

### Recursive solution to the extended Josephus problem

The Josephus Problem is described here, with extension of killing every $k$th problem. In the simple case where every other person is killed, we can also use the binary trick. ...
0answers
46 views

### What do indices in brackets mean? [closed]

Solving the Schrodinger equation for a free particle gives me this output: What does the $\psi^{(2,0)}$ mean here?
1answer
27 views

### Creating a tensor of rank $k$ from elements of a list

Given a list containing $4^k$ elements, how do I create a "square" $\underbrace{4\times...\times4}_{k\text{-times}}$ tensor of rank $k$? Intuitively, I would opt for the ...
3answers
379 views

### Count number of occurences of particular numbers in list

I have a list of numbers which I have rounded and now all numbers are divisible by 5. ...
1answer
36 views

### Contour plot of data

I have two vectors (plain lists), say a,b, from which I generated a 2d table, say mat. It's not a direct expression like ...
1answer
51 views

### ErrorListPlot (in ver. 12) and double-Y plots [duplicate]

Both of my questions concern ListPlot, so I hope it is acceptable to ask them both in one post. ErrorListPlot seems to have ...
0answers
24 views

### Creating all possible $n$-touples of indices in order to output a tensor of arbitrary rank $n$? [closed]

I have a function T[i_, list_List], that accepts a matrix of dimension $2^n \times 2^n$ and $n$ indices $\in \{0,1,2,3\}$ and outputs the corresponding tensor ...
1answer
29 views

### Extending a piecewise function defined over a limited domain to be periodic over a larger domain

I need to plot the piecewise function $\qquad f(x) = x^2\quad -2 <= x <= 0, \\ \qquad f(x) = 0\qquad 0 <= x <= 1 \\ \qquad f(x) = 1-x\quad 1 <= x <= 3 \\$ as a periodic ...
1answer
226 views

### Speed up a distortion of 4k image

I want to undistort 4032 x 3024 image with OpenCV model using only radial distortion. This model is described here. The main issue is the speed. I have a function ...
0answers
33 views

### Plotting matrices

I have this expression: $\int g^{m \bar{n}} g^{r\bar{p}} \partial_t {g}_{m r} \partial_t {g}_{\bar{n}\bar{p}} ~ d^6 y = f(t)$ Where m,n,p,r=1,2,3 and the $\bar{}$ ...
0answers
24 views

### Unknown option ContentSize for Labeled? [closed]

I am (desperately) trying to get my labels smaller, but the ContentSize option does absolutely nothing to my 'Labeled' function, and I get the error message "Unknown option ContentSize for Labeled" ...
0answers
34 views

### How to find the value in which an expression becomes greater than another

I have the following expressions: $\Delta \sigma_1=\frac{2 \gamma ^2 \left(\text{$\sigma $Y} \log \left(\frac{\gamma }{\alpha }\right)+\text{pe}\right)}{\left(\gamma ^2-1\right) \rho ^2}$ \$\Delta \...
1answer
42 views

### An extraneous line appears in the printed version of a Mathematica-image in a pdf-document

My system/workflow Mathematica version 11 MikTeX 2.9: tex->dvi->ps->pdf->paper I have run into the following difficulty. I cannot tell whether the problem is caused by Mathematica, MikTeX, Adobe, or ...
2answers
129 views

### NIntegrate doesn't work with NumericQ

Usually it is advised to use NumericQ to avoid symbolic evaluation in NIntegrate. Here I'm trying to use NumericQ, but the NIntegrate gives an error: ...
1answer
17 views

### Alignment when not dealing with (just) text [duplicate]

In designing interfaces for dynamic operation, I am finding that I cannot figure out how to get alignment to work. For example: ...
0answers
34 views

### Mathematica (v12.0) fails to Import NASACDF (Common Data Format)

I was doing research about Mars using data from MAVEN spacecraft. The data used could be downloaded from https://lasp.colorado.edu/maven/sdc/public/data/sci/swe/l2/2017/06/. When run ...
1answer
92 views

### How to get the implicit solution of this PDE (Maple can but I don't manage with mathematica)?

I asked this question about the analytical solution of the PDE: $$\partial_t c=\partial_x((c-a)(c-b)\partial_xc)$$ And I was given the answer that Maple gives the following implicit form as a ...
1answer
73 views

### How to use function as a placeholder for codes

I want to use function as a placeholder for a bunch of codes while making the function also produce an output Consider A={0,0,0}; f[x_]:=Block[{},A[[x]]=1;A] f[1] ...
1answer
32 views

### Chaining NetGraphs

I have two NetGraphs, each with 3 different input ports ("Input","Random1","Random2"), the first with 2 outputs ("Output" and "Loss") and the second with one output "Final_Out". All I want to do is "...
0answers
44 views

### What row do I change to make my determinant non zero?

I wish to make a matrix that has an inverse. I need rows that look like oscillating functions so I decided to base my matrix on ChebyshevT. This code makes an n by ...
1answer
97 views

### ParametricNDSolve fails when I *don't* print the results

Some updates added to end. Truly minimal exampled added at top. Minimal example: ...
0answers
50 views

### How to display rotated columns names in dataset?

Consider the following minimalist Dataset: ...
0answers
12 views

### Weird interaction between RegionFunction and MaxRecursion

Compare the two following outputs: ...
2answers
81 views

### Solving of Equation which contains Hypergeometric Function 2F1

I am trying to solve this equation where I need the solution of K in term of v ...
1answer
50 views

### Remove ticks from chart labels

Given the following chart: BarChart[{{1, 2, 3}, {4, 5, 6}}, ChartLabels -> {{"r1", "r2"}, None}] How can I remove the ticks of the chart labels (marked with ...
3answers
275 views

### Changing Row Keys into Normal Rows

I have a dataset with column and row keys: ...
2answers
44 views

### How to obtain a variable in terms of another variable?

I'm new to Mathematica and would like to ask a question about equation systems. I have a linear equation system given in the link. I would like to obtain kappa1 in terms of psi1, kappa2 in terms of ...
0answers
28 views

### MorphologicalTransform: What is the difference between EndPoints and SkeletonEndPoints?

What is the difference between the "EndPoints" and "SkeletonEndPoints" functions of ...

15 30 50 per page