16
votes
4answers
2k views

What is the right way to rotate an array?

Suppose I have an array, not necessarily square: a = $\left( \begin{array}{ccc} 1 & 2 & 3 \\ 4 & 5 & 6 \\ 7 & 8 & 9 \end{array} \right)$ I want to rotate it like one ...
14
votes
3answers
1k views

How can I tell mathematica to generate an histogram from nominal data?

If I write: Histogram[{1, 1, 1, 2, 2, 2}] I get a nice histogram chart but if I write ...
14
votes
3answers
972 views

Constructing a symbolic Hermitian matrix

I need to construct a symbolic Hermitian matrix like m = { { n, a, b, b}, {Conjugate[a], n, b, b}, ... } but I am not able to set ...
13
votes
2answers
525 views

How can I get LineLegend to pick up my plot's BaseStyle?

The new legends functionality in version 9 really simplifies creating legends, and it automatically picks up the styles of the lines. ...
13
votes
2answers
413 views

Anti-aliasing with the multiple-object form of Polygon?

Observe: rand = RandomReal[1, {4, 3, 2}]; Graphics @ Polygon @ rand Graphics[Polygon /@ rand] I am losing ...
12
votes
1answer
181 views

possible bug in Mathematica TeXForm? Generating \left\left

I asked about this in the TeX chat. It seems Mathematica generate invalid Latex in this example. ...
12
votes
2answers
1k views

Using a ListDensityPlot to map color onto a ListPlot3D graph

I have a 3 column list of data points. The first two columns correspond to x and y coordinates, with data points creating a surface in the z direction from column 3. This gives me a nice wavy ...
12
votes
4answers
4k views

Minimizing a function of many coordinates

I'm trying to obtain a series of points on the unit sphere with a somewhat homogeneous distribution, by minimizing a function depending on distances (I took $\exp(-d)$). My points are represented by ...
12
votes
3answers
750 views

NIntegrating within an Ellipsoid

I need to numerically integrate an expensive positive-definite function over a 2D domain. I know by other ways that the function is basically zero for values outside the following ellipse: ...
12
votes
6answers
2k views

How do you skip missing data values in a data file?

In scanning through a simple imported file of weather station data, some dates have missing data. What is a test to use to check whether a datum is valid? I tried ...
12
votes
1answer
369 views

Why is MainEvaluate being used when LinearSolve can be compiled?

According to this question LinearSolve can be Compiled. However, CompilePrint shows a MainEvaluate but no-warning is generated. It appears that LinearSolve is not ...
11
votes
1answer
244 views

BUG: AssociationMap loses definition

I'm facing a strange behavior of AssociationMap. With a fresh Kernel session: ...
11
votes
3answers
704 views

Change the inner color of markers

I would like to have a marker with white as its inner color, to be able to make this kind of graph: If I use PlotMarkers -> Style["\[FilledSquare]", White], ...
11
votes
4answers
381 views

“Strange” behavior of Rule

According to the Help lhs->rhs evaluates rhs immediately. How to understand the output of the following code? ClearAll@x; {1, 3.5} /. x_?IntegerQ -> {x} ...
11
votes
2answers
266 views

Is it possible to create Evaluatable cell which will be automatically overwritten?

Am trying to generate an Evaluatable cell which itself is an output cell which will be overwritten when the original Input cell ...
11
votes
1answer
340 views

Using non-trivial objects in RLink

I would like to use RLink to access igraph, which has an R interface. I do not know R; my motivation for learning it is to be able to access igraph easily. I installed igraph using ...
11
votes
3answers
3k views

Saving high-quality graphics through commands

Say I make and display a graph in a Mathematica notebook: graph = CompleteGraph[100] If I drag the corner of the graph to increase its size, and then save it to ...
10
votes
3answers
262 views

balanced Shortest[] and string-patterns

The pattern Shortest["A"~~__~~"B"] is oriented : It assumes the text is read from left to right and it takes the text between the first "A" and the next "B". Any ...
10
votes
4answers
1k views

Filling between two 3D surfaces

I know it is possible to create a filling in between two curves on a 2D plot, but is it possible to do the same in 3D? My attempt like this: ...
10
votes
1answer
1k views

Implementing OCR without using TextRecognize

I am new to Mathematica and trying to figure out whether it is a good tool for algorithmic exploration. So I had the idea of implementing a simple OCR with Mathematica, just using standard ...
10
votes
3answers
538 views

Programmatically quitting the FrontEnd or running without one?

I have a conundrum. I use an iMac's OS X 10.6.8 settings to start and stop the machine at the specific times that I need a particular notebook to run. I've done this because it has worked more ...
10
votes
1answer
776 views

Nesting Parallel processes

I just attempted to run code that had nested ParallelMap[] functions. It generates the error message: ParallelMap::subpar: Parallel computations cannot be nested; proceeding with sequential ...
9
votes
1answer
251 views

Bug in handling backslashed Cyrillic symbols in v.10.0.0?

Consider: "\бвгд" // FullForm "\\бвгд" // FullForm In v.8.0.4 I get this: ...
9
votes
1answer
630 views

Uniformly distributed n-dimensional probability vectors

What's the right way to generate a random probability vector $p={p_1,\ldots,p_n} \in {(0,1)}^n$ where $\sum_i p_i=1$, uniformly distributed over the $(n-1)$-dimensional simplex? What I have is ...
9
votes
1answer
202 views

Structure of Graphics (esp. those produced by Plot, ListPlot, etc.)

I'm looking for a description of the structure of Graphics objects, aimed at the advanced Mathematica programmer. The motivation for this question is the ...
9
votes
2answers
389 views

Tailoring RegionPlot3D with PlotPoints?

This seemingly tame solid gives Mathematica (v9) a bit of a workout if you want to generate a good picture: ...
9
votes
7answers
396 views

How to efficiently Append a result of an operation on each element of a list to itself

I'm looking for the best function to apply the product of the last two elements of sublist elements to each element: Example: ...
8
votes
7answers
732 views

Populate an upper triangular matrix from a vector of elements

What is the best way to populate an upper triangular (or alternatively: lower triangular or symmetric) matrix from a vector of elements? This example input: ...
8
votes
4answers
435 views

Gather list elements by index

The following list has some elements that are labeled. For example {1, 2} -> 1, {-1, 3} -> 3, etc: ...
8
votes
3answers
595 views

How do I make Reduce yield all solutions explicitly?

Say I want to do the following: Reduce[ x+y+z==1, {x,y,z}, Modulus -> 7 ] then I get a solution with parameters, C[1] : ...
8
votes
2answers
343 views

How do I get the equivalent of the $\LaTeX$ \tag{} in Mathematica?

How do I get the equivalent of the $\LaTeX$ \tag{} in Mathematica? $a+b=x \tag{1}$ I'm not necessarily asking how to use the $\LaTeX$ \tag{} itself in ...
8
votes
1answer
964 views

How do I expand a sum?

I have a problem with Mathematica's symbolic manipulations. As an example, consider the following expression: $$\sum _{i=1}^n -2 x_i \left(-a x_i-b+y_i\right)=0$$ How do I get Mathematica to expand ...
8
votes
3answers
1k views

Discrete Convolution

Ask to compute the convolution of 2 lists, I managed to do so, with what I feel is rather heavy : Let my 2 lists be : a = {1,2,3,4} b = {1,1,1,1,1,1}; The below function adds 0s on each part of ...
7
votes
3answers
322 views

Generating a polynomial that's accurate to within an error of no more than 1/10^5

I'm currently stuck on a question for class that asks... "Find a polynomial p[x] that you can use to calculate 6 ArcTan[x] to ...
7
votes
1answer
203 views

Is there a faster way to Map an Association?

Consider mapping an existing Association in a manner such as this: ...
7
votes
6answers
2k views

How do I draw a hemisphere?

I want to draw a solid or partially transparent hemisphere above a partially transparent cuboid object in Graphics3D. However, I do not know how to do this s.t. only half the sphere is drawn. Here's ...
7
votes
1answer
333 views

Crash when displaying / rasterizing graphics with textures at high resolutions

CAUTION/Disclaimer: execution of some of the code below can result in a complete crash of Mathematica or even your system. Save all your work and do not try in a productive situation. For a graphical ...
7
votes
3answers
262 views

Wrapping EventHandler by Table

I am making a grid on the screen. The grid is composed of different expressions. I want all of them to have a Gray background, which turns into a ...
7
votes
1answer
2k views

How to run a Mathematica program using command line on windows?

I have to run some Mathematica programs on a remote computer running the Windows XP operating system. However, I do not know how to run the program using the command line on this system. What do I ...
7
votes
2answers
256 views

Clean up list of partial outputs for memory

Context I run long Mathematica sessions; sometimes I have Output up to Out[3000+]. Hence I would like to be able to clear out some previous outputs which do use lots of memory. Attempt I am aware ...
7
votes
1answer
3k views

How to extract sample values from an imported WAV file?

Suppose I read a file with B = Import["something.wav"] Now how can I obtain a list of sample values?
6
votes
2answers
2k views

How to reverse the direction of the y axes

I have a similar question to this one. Unfortunately, the answers there didn't help me. I would like to plot a simple function with the normal Plot function. ...
6
votes
1answer
540 views

Hatched bars and bar-specific background in BarChart

I would like to diagonally hatch the bars in BarChart and to have three different background colors for the different bars, like this: Any ideas how to ...
6
votes
2answers
583 views

Slice through Graphics3D

is there any possibility to slice through a Graphics3D object? At the end I would like to have a stack of images slicing , e.g. $n$ times in $z$-direction: $((x,y,z_{0}), (x,y,z_{1}),…,(x,y,z_{n}))$ ...
6
votes
2answers
201 views

Evaluating selected expression using keyboard shortcut

Imagine that in this toy code I want to evaluate just the selected (blue) expression: To get as output result: {09/14,09/15,09/16,09/17,09/18,09/19,09/20} There is some shortcut to do this? I'm ...
6
votes
3answers
495 views

Opacity and overlapping multiple polygons

Let's say I have 100 polygons that are all different but most of them overlap. All I want to do is to draw/plot them in one single graphic with linearly adding gray values; i.e., a point with ...
6
votes
4answers
876 views

How to apply a function to a list of tuples

trialList = {{0, 24.701}, {1, 24.69}, {2, 24.733}}; f[x_] := x + 1; I would like to apply the function f to only the second ...
6
votes
1answer
1k views

Why does Plot leave gaps in the graph of a continuous function? [duplicate]

I have plotted the overlapping area of the UnitBox and the triangle function as: ...
6
votes
1answer
197 views

Is it possible to render Graphics with more than “Byte” bitdepth?

I wonder is it possible to render Graphics in Mathematica with bitdepth higher than "Byte" which is the maximum bitdepth ...
6
votes
3answers
1k 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 ...

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