================================== Top new questions this week: ==================================
[Terrifying performance decrease for contour/density plots in v10.1 -> 10.3] http://mathematica.stackexchange.com/questions/99255/terrifying-performance-decrease-for-contour-density-plots-in-v10-1-10-3
I setup for download a test dataset at http://www.inrim.it/~magni/cm.dat.gz (a set of 64800 triplets x,y,z).
The behavior can be reproduced with the following code:
link = ...
- asked by alessandro (24 votes), answered by Jason B (13 votes)
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[Cyclic Take function?] http://mathematica.stackexchange.com/questions/99188/cyclic-take-function
Is there some direct and simple "cyclic Take", sometimes also known as "overtake" in Mathematica. That is, if the take specification runs out of elements, it just cycles back to the beginning (as many ...
- asked by murray (21 votes), answered by kglr (22 votes)
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[Speeding up generation of block diagonal matrix] http://mathematica.stackexchange.com/questions/99467/speeding-up-generation-of-block-diagonal-matrix
I’m struggling with the following problem. I have \(48\) square matrices (full, filled with real machine precision numbers, thus are packed, all different) of size \(128\). I wolud like to place them on a ...
- asked by mmal (16 votes), answered by ybeltukov (14 votes)
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[Integrate returns imaginary answer for smooth, real function] http://mathematica.stackexchange.com/questions/99395/integrate-returns-imaginary-answer-for-smooth-real-function
Bug introduced in 7 or earlier and persisting through 10.3
I’m trying to evaluate the integral:
\[\int _0^{\infty } \frac {1}{4 b \sqrt {\pi } r} e^{-(b-r)^2}(e^{4 b r} - 1) \mathrm {d}r\]
with ...
- asked by Kevin Driscoll (15 votes)
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[Detecting an ellipse in a glaucoma photo] http://mathematica.stackexchange.com/questions/99578/detecting-an-ellipse-in-a-glaucoma-photo
For glaucoma diagnosis it is common to determine a "cup to disk ratio" which compares the diameter of the optic disk (VDD) and optic cup (VCD). The optical disk is visible as a circular red feature ...
- asked by indra ginanjar A.T (14 votes), answered by belisarius has settled (17 votes)
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[How to implement the general array broadcasting method from NumPy?] http://mathematica.stackexchange.com/questions/99171/how-to-implement-the-general-array-broadcasting-method-from-numpy
A friend of mine introduced array broadcasting in the Python NumPy package which is very convenient (and also highly efficient).
The idea is perfectly shown in this picture:
Basically, the method ...
- asked by matheorem (14 votes), answered by Pillsy (15 votes)
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[Derivative of a pure function with SlotSequence] http://mathematica.stackexchange.com/questions/99439/derivative-of-a-pure-function-with-slotsequence
I can live with this but I can’t figure out why the following is 0:
Derivative[1][f[##] &][x] 0 From documentation for Derivative: [...] Whenever Derivative[n][f] is generated, the WL ...
- asked by Kuba (14 votes), answered by Michael E2 (13 votes)
================================== Greatest hits from previous weeks: ==================================
[Even Fibonacci numbers] http://mathematica.stackexchange.com/questions/37266/even-fibonacci-numbers
Today, I found the Euler Project. Problem #2 is
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
1, ...
- asked by Shutao TANG (26 votes), answered by rcollyer (34 votes)
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[How can I plot the direction field for a differential equation?] http://mathematica.stackexchange.com/questions/8841/how-can-i-plot-the-direction-field-for-a-differential-equation
I’d like to plot the graph of the direction field for a differential equation, to get a feel for it. I’m a novice, right now, when it comes to plotting in Mathematica, so I’m hoping that someone can ...
- asked by Matt Groff (16 votes), answered by Peter Breitfeld (13 votes)
================================== Can you answer these? ==================================
[Odd Coloring with GeoRegionValuePlot] http://mathematica.stackexchange.com/questions/99478/odd-coloring-with-georegionvalueplot
When I’m plotting data with GeoRegionValuePlot, I’m getting some strange coloring errors:
The grid included shows the top 10 countries with arable land per population. However, Australia is colored ...
- asked by DavisDude (1 vote)
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[Find regions in which the roots of a third degree polynomial are real] http://mathematica.stackexchange.com/questions/99167/find-regions-in-which-the-roots-of-a-third-degree-polynomial-are-real
I have to find the roots of a third degree polynomial in \(\phi \) that depends from 3 parameters, namely \(t,s,w\in \mathbb R\). In order to do that I’ve used the command Solve, in the following way:
...
- asked by Claretta (5 votes)
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[Works with example numbers, but not with variables alone] http://mathematica.stackexchange.com/questions/99575/works-with-example-numbers-but-not-with-variables-alone
The following code prints the correct solution for variable a (2.23). But if i comment out the 5 given example numbers on top it fails. If i remove some of the constraints at the bottom (&& ...
- asked by JoDo (1 vote)