4.26 Tuesday, June 27, 2017

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Top new questions this week: 
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[Display 10^n as power] https://mathematica.stackexchange.com/questions/148794/display-10n-as-power

How can I tell MMA to display input of the form 10^n as \(10^n\) and not e.g. as 1000 for \(n = 3\) or the rational \(\frac {1}{1000}\) for \(n = -3\).

This would help to keep tables compact when some ...

- asked by Casimir (13 votes), answered by eldo (10 votes)

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[How to remove unknown zero-width character from string?] https://mathematica.stackexchange.com/questions/148899/how-to-remove-unknown-zero-width-character-from-string

I have text that contains a zero-width character that I am not able to remove. A minimum example is in str below where the character is at the start of the text.

str = "4-6"; 
res = ToExpression /@  ...

- asked by Edmund (12 votes), answered by Carl Woll (10 votes)

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[Series sum approximation] https://mathematica.stackexchange.com/questions/149090/series-sum-approximation

Since there is no closed formula, as far as I know, to find the sum of

\[\sum _{n=2}^{\infty } \frac {(-1)^n}{\sqrt {\log (n)}}\]

I used //N to find an approximation and Mathematica gave me ...

- asked by Raffaele (11 votes), answered by TeM (18 votes)

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[How to extract first 9 rows from every block of 22 rows?] https://mathematica.stackexchange.com/questions/149026/how-to-extract-first-9-rows-from-every-block-of-22-rows

I’m working with a list of lists (a large table).

How would I extract the first 9 rows from every 22 rows of this list?

Essentially, I’d like to drop rows 10 to 22, and then 32 to 44, and so on, ...

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

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[Confusion about HoldFirst attribute of Set] https://mathematica.stackexchange.com/questions/148956/confusion-about-holdfirst-attribute-of-set

Set has the attribute HoldFirst. Expectedly the following does not work, i.e. it does not assign the OwnValue of 3 to x:

In[1]:= {x, y}[[1]] = 3 
 
During evaluation of In[1]:= Set::setps: {x,y} in the  ...

- asked by kalix (8 votes), answered by Kuba (10 votes)

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[What algorithm is Mathematica using to find the smallest eigenvalue so quickly?] https://mathematica.stackexchange.com/questions/148759/what-algorithm-is-mathematica-using-to-find-the-smallest-eigenvalue-so-quickly

My question is what kind of black magic is Mathematica doing to obtain the correct answer so quickly compared to other programming languages?

Details:

I’ve written a Mathematica notebook to find the ...

- asked by Daniel Walsh (8 votes)

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[Simplify expression with Sqrt] https://mathematica.stackexchange.com/questions/149186/simplify-expression-with-sqrt

Hi folks I have a simple Simplify[] question

the following expression simplifies nice:

Sqrt[4 (a + b) - 4 c] // Simplify 
2 Sqrt[a + b - c] 
 
 
the next one refuses 
 
Sqrt[4 (a + b) - 4 (c + d)] //  ...

- asked by Robert Nowak (6 votes), answered by Shadowray (5 votes)

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

[Calculate the 2D Fourier transform of an Image] https://mathematica.stackexchange.com/questions/29203/calculate-the-2d-fourier-transform-of-an-image

I am new to Mathematica, and using version 8.0.

I would like to calculate the 2D Fourier Transform of an Image with Mathematica and plot the magnitude and phase spectrum, as well as reconstruct the ...

- asked by user8727 (5 votes), answered by Nasser (27 votes)

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[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)

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

[Cross-section of graph] https://mathematica.stackexchange.com/questions/148902/cross-section-of-graph

I am trying to use the following code to plot the cross-section 
of the graph z=x^2+y^2 and x=t. I use Manipulate to vary t. 
 
h = z - x^2 - y^2; 
g = x; 
Manipulate[ 
 Show[ 
  ContourPlot3D[{h == 0, g ==  ...

- asked by henryforever14 (1 vote)

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[How to embed Mathematica or Wolfram Alpha results in a website] https://mathematica.stackexchange.com/questions/149063/how-to-embed-mathematica-or-wolfram-alpha-results-in-a-website

Is it possible to dynamically embed responses into a blog post?

So the user would see:

There are 390900 plant species in the world.

With pseudo code:

There are #{worlfram(number of plant species)}  ...

- asked by Mr. Demetrius Michael (1 vote)

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[Package MathWorld] https://mathematica.stackexchange.com/questions/148837/package-mathworld

I’m looking for MathWorld packages, but I can not find anywhere. I found an question that came very close but did not help me.

I got lost on the site and did not find anything.

I need to use the ...

- asked by LCarvalho (4 votes)