6
votes
2answers
174 views

DeleteMissing level spec confusion

Given: titanic = ExampleData[{"Dataset", "Titanic"}] Why does this correctly delete Missing[] elements: ...
6
votes
3answers
906 views

Converting a string containing whitespace-delimited numbers to a list of numbers

Suppose I have a string str that contains only whitespace-delimited real numbers: ...
6
votes
2answers
263 views

Graph does not evaluate some options when not displayed

How can I force Graph to evaluate all its options without actually displaying the graph itself? Evaluating the following code ignores the ...
6
votes
2answers
334 views

Diagonals of a regular octagon

We had a little activity after school today and one of the questions was: All diagonals are drawn in a regular octagon. At how many distinct points in the interior of the octagon (not on the ...
6
votes
1answer
114 views

Synchronizing Dynamics with EventActions ( and other preemptive evaluations)

I would like to make a simple "game": Display a dialog with a random letter, if the same letter is pressed on the keyboard, the display changes into a string ...
6
votes
2answers
338 views

Cannot Get Numerical Results to Match

I try this numerical summation (in two parts) ...
6
votes
1answer
94 views

Problem Using Evaluated Replace with Associations

If I define some function like: toISOdate[data_List]:=DateString[data,{"Year","-","Month","-","Day"}] and try to applicate it in an ...
6
votes
4answers
1k views

Select a repeated element in a list

I want to select all elements that repeat 4 times in the list. I propose this code ...
6
votes
1answer
562 views

Parallel optimization of Markov Chain Monte Carlo

I'm trying to reduce the computation time of a MCMC simulation. Essentially I have a set of particles performing a random walk in a periodic random potential. The particles are independent and every ...
6
votes
1answer
3k views

Is it possible to generate a Hasse Diagram for a defined relation?

I'm looking for a way to create a Hasse Diagram from a given partial order binary relation. The relation will be given explicitly, for example: ...
6
votes
2answers
571 views

How to overload System`StringJoin to automatically use ToString on arguments?

I am using an overloaded version of the StringJoin function since years now, without any problem, as I've invested a lot of time and effort earlier to make its ...
6
votes
1answer
451 views

Representative Smooth Kernel Distribution from Truncated Distribution

I am trying to produce a better distribution from a dataset that is bounded to be greater than 0. Here is an example distribution from the documentation that mimics the behavior of the actual dataset: ...
6
votes
1answer
232 views

Keeping vertexcoordinates after adding a new vertex

I want to add a new vertex to a graph, with fixed VertexCoordinates but when I use VertexAdd, the new graph does not have the VertexCoordinates of the previous one. ...
6
votes
2answers
741 views

Fitting data to an ARProcess using FindProcessParameters

I have 50 data points that I would like to represent as an AR(4) process. I'd like to over-plot the behaivor of the estimated process model with that of the original (raw) data before I use the model ...
6
votes
2answers
444 views

How do I plot my country map with weather data stations?

I've tried this code, but I can't plot the coordinates in my country map. ...
6
votes
3answers
540 views

Finding connected components in an array

I have an $w\times h$ array with non-negative integers. I wish to partition the set of coordinates $(c,r)$ with $1\leq c \leq w$ and $1\leq r \leq h$, in subsets, so that each subset corresponds to a ...
6
votes
3answers
541 views

How do I find the amount of free space on disk?

I know a workaround, where one calculates sizes of all files and then you subtract this from your default space, but is there any direct way to do it? Simplicity and speed are important. There's the ...
6
votes
3answers
2k views

Spreading colors in ListDensityPlot

I want to create a two-dimensional plot using data from an external file. This file contains several triplets of numbers. The first two columns indicate the x and y position, while the third one works ...
6
votes
3answers
4k views

Mathematica function intersection points with 3D grid

I need to produce a 3-dimensional equispaced grid over a given function in a way, that I can calculate intersection points of the function with the grids edges. So my first question is how to produce ...
6
votes
1answer
2k views

Export Table from Mathematica into specific cells Excel

How can I export a table to Excel - to specific cells, e.g. D1-E2? Background: I want to compare results, and it's easier to have the results on one spreadsheet. I'm using Mathematica 6. This is my ...
6
votes
1answer
1k views

Formatting output of OpenAppend[] to match what Export[data,file,“.csv”] would output?

I have a large data set that gets exported to a .csv file. Export[data,filename,"csv"] is extremely fast and formats the data in a nice JMP-friendly manner. However,...
5
votes
4answers
188 views

Performance: Collapsing repeated contiguous rows & cols from a matrix

In this answer I needed to remove contiguous zero-valued cols and rows from a matrix, leaving only two of them in place, no matter what the original number was. I made up this code: ...
5
votes
1answer
154 views

Multidimensional arbitrary precision spline interpolation on the grid

This question is a generalization of the previous one for multiple dimensions. In the answer to that question an implementation for the clamped spline interpolation for 1D case and arbitrary degree of ...
5
votes
4answers
126 views

Solving an equation with rational expressions (step by step) [duplicate]

Consider the following equation with rational expressions: $$\frac{5}{x+4}=4+\frac{3}{x-2}$$ We will look at the plot. We will use the Solve command to check our answer. ...
5
votes
4answers
240 views

How should I deal with messages being produced by my Manipulate?

I have made a knockoff of John Polking's dfield for a web-embedded CDF (via Enterprise Mathematica). My code extends that from Belisarius who last year showed me how to use ...
5
votes
1answer
190 views

Ordered associations

Mathematica 10 has introduced Associations, elsewhere known as hash tables or dictionaries. Is there Ordered equivalent like in Python, Java, .NET? The data structure should remember the order in ...
5
votes
4answers
321 views

HoldForm does not Hold Form for fractions sometimes

I'm facing a strange behavior of HoldForm. I need to display 1/2*3/4 in LaTeX like this : $$ \frac{1}{2} \times \frac{3}{4} $$ ...
5
votes
3answers
383 views

Histogram of a very large dataset?

I have a very large dataset stored in a file (over 2GB). The file contains a tab-separated table of floating-point numbers. I want to do an Histogram of all the numbers in the table. But if I try to ...
5
votes
2answers
373 views

How to fold output cells by default?

In Mathematica the default behavior of output cells is to pop up after the kernel has processed the input cells and got a result. I know I could add ; in the end of ...
5
votes
3answers
678 views

Is Table the only functional way to construct nested loops in Mathematica?

Suppose you have a cubic box containing identical particles and you want to compute the distances between each particle and every other particle in the box without double-counting (i.e., if you've ...
5
votes
2answers
179 views

Capturing an F1

I teach an Intro to Mathematica course, and one of the things I try to reinforce early on is just how helpful Mathematica's help is. In the very first lab for the course, I even give the students a ...
5
votes
1answer
142 views

Inaccurate Heliocentric coordinates of PlanetaryMoonData

I have noticed that the heliocentric coordinates obtained with PlanetaryMoonData are very inaccurate. Fore example, consider the Galilean moons of Jupiter: ...
5
votes
1answer
369 views

Getting all physical units with prefixes

How we can get the list with all physical units and prefixes from WolframAlpha and make symbols from the result to be equal their corresponding quantities like described in this post?
5
votes
3answers
230 views

How to get the coordinates of the intersection of two lines from a ListLinePlot?

Suppose I have two curves intersect at some point, how can I read the coordinates from the graph, not read by eye, but find it with more precision by computer. For example, here are two lists created ...
5
votes
1answer
559 views

Why is there a huge performance gap using Map with more than 100 List entries

im using Map on a List like this: cube= {{1, 1, 1}, {1, 1, 2}, {1, 1, 3}, {1, 1, 4}, ... , {5, 5, 4}, {5, 5, 5}} Mapping the whole List with 125 entries takes ...
5
votes
1answer
347 views

Embedding StreamPlot in Graphics3D

I am trying to visualise the action of the infinitesimal generator of a Lie group on the solution of a 2-ODE system drawn in the 3D space (t,y1,y2): t is time and y1,y2 are the two dependent variables....
5
votes
1answer
668 views

CUDALink is not initialized

I've upgraded to Mathematica 9.0 on Ubuntu 12.04 with the latest Nvidia driver (304.64). I load CUDA by using, as usual, Needs["CUDALink`"]. ...
5
votes
1answer
100 views

Possible to include additional styles in context menu?

I am using Mathematica 9 on Windows 8, and I regularly want to use cell styles such as Section, SubSection and so on. If I click the + button before creating a new ...
5
votes
3answers
2k views

Replace function and its derivatives found with Solve

If I have an equation eq = f[x] + g[x] == 0 and I solve for f[x] sol = Solve[eq,f[x]] ...
5
votes
2answers
9k views

How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc

I'm trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example, ...
5
votes
2answers
614 views

How to extract RGB arguments as a list

Although the following lines of code work fine they are very awkward. My questions are below a = RGBColor[1, 0, 0] b = RGBColor[0, 1, 0] Is there a more compact ...
5
votes
2answers
279 views

Implement functions that depend on previous value in NDSolve

I want to numerically solve a system of differential equations in Mathematica, say for example $\frac{dx}{dt} = f(x,y,t) \\ \frac{dy}{dt} = g(x,y,t)$ for $x(t), y(t)$. However, the functions depend ...
5
votes
2answers
760 views

Triangle mapped on a sphere in $\mathbb R^3$?

How can I map a triangle on a sphere? I want to visualize (plot or animate) it for my student in Non-Euclidean geometry. I have no restrictions on the triangle's kind or on the sphere in $\mathbb R^3$....
5
votes
1answer
904 views

Reduce an equation by putting a new variable

I have the following equation given: $$ (26-x)\cdot\sqrt{5x-1} -(13x+14)\cdot\sqrt{5-2x} + 12\sqrt{(5x-1)\cdot(5-2x) }= 18x+32. $$ In order to solve it, I want to substitute $t = \sqrt{5x - 1}-\sqrt{...
5
votes
1answer
469 views

ListPlot3D of a set of points in a non-convex region

I would like to plot a set of points in the same style as ListPlot3D does, but only in a non-convex region that I can specify (e.g. using a ...
4
votes
3answers
625 views

Summation with constraints

I am trying to do the summation shown below, $\sum_{i_1=0}^{imax_1} \sum_{i_2=0}^{imax_2} \dots \sum_{i_k=0}^{imax_k} f(i_1,\dots,i_k)$ $k$ is a variable. Therefore $i$ and $imax$ are defined as ...
4
votes
1answer
646 views

How to dequantify units in mathematica?

Is there a function which applied to a quantity returns its numerical value so I for instance can fill it into my Predictorfunction?
4
votes
2answers
81 views

MatchQ failing in some cases with Hold [duplicate]

Could someone clarify why the first of these MatchQ finds a match whereas the second does not? (I'm using version 10.0, in case that matters.) ...
4
votes
2answers
551 views

Using compiled function inside NMinimize

Consider this code: ...
4
votes
1answer
183 views

Recognize physical constants?

Is there some way to ask Mathematica to recognize physical constants, such as 32 or 9.81 (gravitational acceleration, in different units, at Earth's surface)? I have in mind something like the "...

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