4.21 Tuesday, August 1, 2017

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Top new questions this week: 
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[String operation 1000X slower for special characters] https://mathematica.stackexchange.com/questions/152293/string-operation-1000x-slower-for-special-characters

It seems that the string operation is very slow if we have special characters in the string. Consider this example,

str = 
  StringJoin@ 
   RandomChoice[Join[Alphabet[], ToString /@ Range[0, 9]],  ...

- asked by xslittlegrass (12 votes), answered by Alexey Popkov (12 votes)

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[Making a website with Mathematica] https://mathematica.stackexchange.com/questions/152663/making-a-website-with-mathematica

I know many people here have various websites associated with them and I’m guessing do at least some of the development of that stuff in Mathematica.

I recently fell down that rabbit hole myself, ...

- asked by b3m2a1 (11 votes), answered by C. E. (9 votes)

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[Convert association with list key to nested assocations] https://mathematica.stackexchange.com/questions/152676/convert-association-with-list-key-to-nested-assocations

I have an association that maps x, y pairs to values, for example:

 <|{0, 0} -> "a", {-1, -4} -> "b", {-1, 1} -> "c", {-1, 0} -> "d", {1, 0} -> "e"|>

I want to convert this ...

- asked by 2012rcampion (9 votes), answered by MarcoB (8 votes)

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[Matching (y/x)^u terms wherever the appear in an expression] https://mathematica.stackexchange.com/questions/152559/matching-y-xu-terms-wherever-the-appear-in-an-expression

Mathematica keeps rewriting expressions, so it is hard to figure what pattern to use.

I am trying to replace all occurrences of \(\frac {y}{x}\) by \(t\), but Mathematica re-writes ...

- asked by Nasser (9 votes), answered by aardvark2012 (4 votes)

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[Bulletproofing packages against SetOptions of built-ins] https://mathematica.stackexchange.com/questions/152472/bulletproofing-packages-against-setoptions-of-built-ins

Packages are (obviously) written in terms of built-in Mathematica functions. But many (if not, most) of these functions have options, like Expand, Solve, Compile

While a package is active, the user ...

- asked by QuantumDot (9 votes), answered by Leonid Shifrin (12 votes)

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[How can I offset a curve from the given data points?] https://mathematica.stackexchange.com/questions/152298/how-can-i-offset-a-curve-from-the-given-data-points

I am new to Mathematica programming.

I have a question related to my work with this software.

I have the data points below:

{{128.011, 86.7748}, {128.011, 86.7748}, {128.167, 86.7663}, {128.19,  ...

- asked by Mukidi Lee (8 votes), answered by J. M. (12 votes)

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[Export[..., "tsv"] drops minus signs from Dataset [horrific bug?]] https://mathematica.stackexchange.com/questions/152355/export-tsv-drops-minus-signs-from-dataset-horrific-bug

Toy example:

First, create a Dataset:

data = Dataset[{<|"x" ->  1, "y" -> -2|>, 
                <|"x" -> -3, "y" ->  4|>}] 

Next, export it as a TSV file:

...

- asked by kjo (8 votes), answered by Rolf Mertig (6 votes)

================================== Greatest hits from previous weeks: ==================================

[Entering numbers in Scientific Notation?] https://mathematica.stackexchange.com/questions/36792/entering-numbers-in-scientific-notation

I need to play with a lot of powers such as 10^-3. 1E-3 does not work for it. Is there any short form for it?

- asked by hhh (32 votes), answered by Rahul (43 votes)

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[Creating legends for plots with multiple lines?] https://mathematica.stackexchange.com/questions/4025/creating-legends-for-plots-with-multiple-lines

So I have a graph with multiple lists, for e.g.

data = {{1,2}, {3,4}, {3,5}, {2,3} . . .} 
 
 
If I then do ListLinePlot[Table[{#1,Log[b,#2]}&@@@data, {b,1,10,2}]] I have 
no way to generate a legend  ...

- asked by Eiyrioü von Kauyf (60 votes), answered by Jens (90 votes)

================================== Can you answer these? ==================================

[Obstacle problem for the heat equation] https://mathematica.stackexchange.com/questions/152491/obstacle-problem-for-the-heat-equation

Consider the problem

$$\begin{cases} 
\max\{\Delta u -\partial_t u, \varphi - u \} = 0 & \text{ in } (0,T)\times \mathbb{R}^n \\ 
u(0,\cdot) = \varphi(0,\cdot) & \text{ in } \mathbb{R}^n. 
 ...

- asked by Hiro (3 votes)

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[DateListPlot of multiple time series with data values and legend appearing as the cursor moves over ploted lines] https://mathematica.stackexchange.com/questions/152405/datelistplot-of-multiple-time-series-with-data-values-and-legend-appearing-as-th

This is very similar to my previous question. I want to use "DateListPlot" to visualize multiple time series (n) and see data values and legend as I move the cursor over plotted lines. To begin with, ...

- asked by ramesh (2 votes)

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[Using FindMinimum for a table of functions] https://mathematica.stackexchange.com/questions/152595/using-findminimum-for-a-table-of-functions

I am relatively new to Mathematica and am having trouble with my code running quite slowly. What I am attempting to do is find the minimum value of a function (a chi^2) of one fit variable, but this ...

- asked by nsbd88 (1 vote)