# All Questions

973 views

### Finding a Concave Hull

I have a 3d clustered data: Is there any other way to get concavehull of 3D data points?
1k views

### Computing the genus of an algebraic curve

How-to compute the genus of an algebraic curve in Mathematica ? In my case the algebraic curve is explicitly defined by a polynomial.
420 views

### Dynamic Programming with delayed evaluation

By using dynamical programming, we can save intermediate steps for recursive relations, as in f[n_]:= f[n] = f[n-1] + f[n-2] However, this only stores ...
467 views

### Mathematica Functions from VBA

I'm trying to call Mathematica functions from VBA (Excel) using .NETLink without success. (Yes, I know Mathematica Link for Excel exists. And yes, I know the proper thing to do is buy it. However, ...
557 views

### Count Elements in Image

I have the following image: img1 I'm trying to count al these colored cells and draw a circle around them. I really don't now how I can use SelectComponents for ...
254 views

### Dependent Manipulate sliders

I would like to use dependent sliders in Manipulate. First slider K0 should be independent and varied from ...
939 views

### Correcting a correlation matrix to be positive semidefinite

Does Mathematica have a way to "fix" a correlation matrix that is not positive semi-definite? I looked through the documentation and search the internet but could not find anything.
878 views

### Making a Stock Options Database in Mathematica

I am trying to use Mathematica to create a stock options database of sorts. That is I wish to write a function that imports the option chain of a given stock. Unfortunately Wolfram has yet to put ...
215 views

### Preserving indentation when creating a new line (when editing in a package)

Background: This is the third question in a row of questions about how to make editing packages in the front-end much more bearable (the other two are here and here). It seems that the front end is ...
300 views

### Is it possible to set a timeout for LinkWrite[]?

This came up in relation to this answer Is it possible to set a timeout for LinkWrite? LinkWrite seems to block until the sent ...
679 views

### How to partition a list in a specific way

I have a list: a = {{1, 2, 3, 4, 1, 2, 3, 4}, {5, 6, 7, 8, 5, 6, 7, 8}}; Using Partition and ...
1k views

### Solving an ODE in power series

How do I find a series solution to an ODE? I do not mean taking the Taylor series of an exact solution; I want to solve nasty nonlinear differential equations locally via plug and chug. Surely, that ...
706 views

### Applying an ArrayPlot as a texture to the surface of a cylinder

I would like to apply a matrix plot to the surface of a 3D cylinder. The matrix plot is the output from a custom cellular-automata, and it would be nice to see the lefthand side of the plot connected ...
465 views

### Smoothing ListContourPlot contours

I have some data of type {{x1, y1, f1}, {x2, y2, f2}, ...} and want to do ListContourPlot. However, there is a problem that the ...
153 views

### Converting StringJoin to StringForm inside Hold

Let's say I have a piece of code: Hold[{code1, "asdad " <> ToString[testa] <> " adsd " <> ToString[testb], code2}] (*MWE ofc*) ...
3k views

### Equation of a line that is tangent to a curve at point

A common problem in the derivative section of calculus texts is "find the equation of the line that is tangent to the curve $y = \ldots$ at the point $P$." To find the line that is tangent to \$y = 2 ...
476 views

### How to apply restrictions to the “integrated” variable, when using NDSolve?

I have to integrate an energy along a path. I know the energy at the "beginning" of the path (energy[0]), and I can determine the energy change (gain and loss) ...
1k views

### Simulate MATLAB's meshgrid function

Here is MATLAB's meshgrid. I came up with these implementations in Mathematica: ...
2k views

### How to find the period of an arbitrary mathematical function?

Is there a function to find the period of an arbitrary (possibly complex) function in Mathematica?
1k views

### Morphing Graphics, color and location

I would like to make a small animation : 1-We start with a random distribution of gray points : ...
435 views

### How to split list into disjoint lists?

I wonder if there is any simple way to split a list into its disjoint sublists, e.g. from list={{a,b},{e,f},{b,c},{c,d},{f,g,h}} get a result ...
317 views

### The dangers of SaveDefinitions — should this really happen?

I have been bitten hard by SaveDefinitions -> True. I'll describe in detail what happened below. My questions are: Is this a bug? What is the most convenient ...
1k views

### How to make hollow polyhedra?

I found a version of the Mathematica spikey in 3D printable format (STL) at the Shapeways site that was hollow. Here it is when viewed in MeshLab: You can see there's a bit cut out of the end, and ...
1k views

### Finding the centroid of a disk in an image

I got about 100 images of the sun and have to find the centre of the star in the images. I have binarized the images and used ComponentMeasurementsto find the ...
297 views

### How can I make a notebook with two column layout?

How can I make a notebook with two column layout? Is it possible? I saw something tools could do such thing? Author Tools?
567 views

### How do I replace a missing value in a column with the value immediately above throughout a table?

I have a large table (7000 rows × 17 columns) of terse textual data. In many of the columns, empty entries have been replaced with "." as a marker. Working from the top of the columns downward, I want ...
727 views

### How to splice together several instances of InterpolatingFunction?

I have a set of InterpolatingFunction returned by NDSolve which are valid over different (but overall continuous) domains. How ...
581 views

### Exporting a dashed plot with a color gradient to a vector graphics format ruins the dashing

When exporting a dashed plot with a color gradient to a vector graphics format such as EPS or PDF, the dashing is partly ruined. For example, this command: ...
758 views

### Listing the functions defined in a package

Assume that I know a package's (Context?) name that is loaded. Now I want to list the functions defined in this package. How can I do it? I remember that I found a way once, but I cannot re-find it. ...
578 views

### Built-in Mathematica data: are they cached? how to speed up the loading?

Mathematica has numerous built-in data for science and math. Every first call to a data function in a new Mathematica session will "re-initialize indices" (download the data). Is there a way to store ...
480 views

### How can I add a column into a existing Dataset?

I'm very excited about the brand new Dataset function. I have played with it in Wolfram Cloud, and haven't figured out how can I add a new column into an existing ...
185 views

### Is there a way to make the “Details” section of the documentation expand by default?

By default, the Mathematica documentation opens with the "Details" section collapsed. This is never what I'm looking for — in fact, I've lost count of the times I've sought help on a feature and ...
709 views

Is it by any chance possible to make the Menu key work as one would expect in Mathematica: opening a context menu? The Menu key does nothing in version 7 or 8 on Windows.
437 views

### How to work with characters from CJK Unified Ideographs Extension B correctly?

Background: Recently I'm trying to deal with some Chinese characters which belongs to the CJK Unified Ideographs Extension B block. The motive comes from some further interest following a former ...
288 views

### Method -> {“AxesInFront” -> False} for Graphics3D

I'm aware of two ways to manage positioning of Axes for Graphics3D: AxesOrigin and ...
440 views

### Creating a R DataFrame like construct in Mathematica

I kept getting my data mixed up so I decided to see if I could construct a package adding a R DataFrame like construct to Mathematica. I managed to cobble something together that sort of works, but ...
539 views

### How can I improve my code for drawing a tree?

This code draws a tree, but it's not in the functional style. ...
660 views

### Numerical partial derivative

For a one-variable numerical function, it's simple to calculate the derivative at a point with Derivative as Szabolcs has pointed out before: ...
443 views

I am trying a read a file that's arranged such that there's alternating set of rows containing data that I don't need and data that I need. So for my case the first n lines in the files are useless to ...
4k views

### Standard deck of 52 playing cards in curated data?

I am not sure how to find out what all is included as curated data. For example, are the individual images of each of the 52 cards in a standard deck of playing cards included? If not, is there a way ...
777 views

### Speeding up random walk for many particles

I am trying to speed up this code for many particles to take a random walk. I'm not sure why it is so slow for such a simple task. I got a few hints from colleagues to reduce the precision of the ...
1k views

### Filtering pixels of a certain color

What is the best way to filter an image so that only the pixels close to a certain color are left? I've downloaded some satellite images from the web where a specific pixel color corresponds to a ...
695 views

### How to thread a list

I have data in format data = {{a1, a2}, {b1, b2}, {c1, c2}, {d1, d2}} Tableform: I want to thread it to : ...
236 views

### Usage displays properly only after second call

If I have a usage message containig two-dimensional stuff (subscripts or formulas) and I call the usage, then sometimes I get an improperly formatted output enclosed in "...". Linebreaks are gone, but ...
411 views

### Need help coding/creating a recursive list

I have two lists A and B, each with 99 real numbers. I want to form a list, C, whose ...
222 views

### Is there a way to get AbsoluteTime to correctly report absolute time differences?

Absolute time supposedly reports the "total number of seconds" between two dates, but it does not. For example because of the leap second applied at 2012-06-30T23:59:60Z ...
467 views

### How to monitor the progress of Read?

I use f = OpenRead["largefile.m"] x = Read[f]; Close[f]; to read in a Mathematica expression from a large file largefile.m ...
324 views

### Internal “Periodical” functions in version 7

In version 7 there exist these Internal context functions: ?Internal*Periodical* ...