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2016-05-24 11:41:57 -0500 asked a question Washed out colors when saving plots to file

I try to use the save command with a view of a 3d plot, like

  mypic = implicit_plot3d(x^2 + y^2 + z^2 == distance, (x, -10, 10), (y, -10, 10), (z, -10, 10), opacity = 0.5) +  point3d(vector([0, 0, 0]), color = 'red', size = 10)
mypic.save('mypic.png', compress = false)

but the colors (in particular, the opacities) are washed out. There is no problem right-clicking to save as png from the notebook, but I want to save a bunch of pngs.

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2016-05-19 11:04:35 -0500 answered a question Permutation set acting on another set

Maybe something like this...

A4 = AlternatingGroup(4)
r1 = A4("(1,2) (3,4)")
r2 = A4("(1,3) (2,4)")
r3 = A4("(1,4) (2,3)")
N = A4.subgroup([r1, r2, r3]) # generate normal subgroup
LC = A4.cosets(N, side="left")

elements = []
for i in range(len(LC[0])):
    for j in range(len(LC[1])):
        elements.append( Permutation(LC[0][i]).left_action_product(Permutation(LC[1][j])) )
myset = Set(elements)
myset

Output: {[3, 1, 2, 4], [1, 3, 4, 2], [2, 4, 3, 1], [4, 2, 1, 3]}

2016-05-18 22:31:21 -0500 asked a question Funny ellipse

I am trying to plot an ellipse (using the term loosely). I want the set of points equidistant from the plane defined parametrically by (0, 0, 1) + t(0, 1, 1) + s(1, 1, 1). It is intuitive that this is just the union of two parallel planes. But when I plot, I get an oval...what is wrong? Note that uncommenting to change the vectors gives two planes as expected, furthering my bewilderment.

posvec  = vector([0, 0, 1])
# posvec  = vector([1, 1, 1])
dirvec1 = vector([1, 1, 0])
# dirvec1 = vector([-1, 2, 0])
dirvec1 = dirvec1 / dirvec1.norm()
dirvec2 = vector([1, 1, 1]) 
# dirvec2 = vector([3, 0, -7])
dirvec2 = dirvec2 / dirvec2.norm()

point  = vector([x, y, z])
relpos = point - posvec
disvec = relpos - relpos.dot_product(dirvec1) * dirvec1 - relpos.dot_product(dirvec2) * dirvec2
dis    = disvec.norm()

radius = 10
my_ellipse = implicit_plot3d(10 - dis, (x, -15, 15), (y, -15, 15), (z, -15, 15), opacity = 0.3)
s, t = var('s, t')
my_focus   = parametric_plot3d(posvec + t * dirvec1 + s * dirvec2, (t, -15, 15), (s, -15, 15), opacity = 0.3, color = 'red')

my_pic = my_focus + my_ellipse
my_pic
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2015-11-10 13:44:38 -0500 asked a question Annoying folding behavior

SageMath cloud folds my cell content sometimes. That is, it hides the code after generating the content. Sometimes, I can unfold by double-clicking, but not always. Am I missing something?

Also, whenever I evaulate a cell in the cloud, my cursor moves to the bottom of all cells. Is there a way to prevent this?

2015-11-10 13:44:38 -0500 asked a question Comments with SageMath Cloud

How to comment/uncomment a block of text with SageMath cloud? Apparently, this can be done with the notebook...for now I am just using an external editor.

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2013-09-06 15:54:58 -0500 asked a question notebook: localhost 8080 vs 8000

I used Sage v. 5.0 for the first time in a while and couldn't connect to the notebook. I received the message: Firefox can't establish a connection to the server at localhost:8000.

I was still able to use Sage from the command line, but decided to install v. 5.11 to see if that would fix my problem.
In fact, it did; and now the notebook opens at localhost:8080.

Does anyone know the reason for this?

2012-09-20 16:18:07 -0500 asked a question Latex formatting for exponential numbers

I noticed that tick_formatter = 'latex' fails for very small/large numbers. Does anyone know a solution to this?

Thanks in advance,

TJ

2012-09-17 15:28:51 -0500 asked a question Precision of find_root

Here is a straightforward question:

I am wondering about the precision of find_root. Looking into the documentation (I'm using Sage v. 5.0), there is a comment along with one of the examples that the "precision isn't very good on some machines." At the same time, it says that the routine converges unless it throws an error.

A post response from William Stein clarifies that the function is passed to SciPy which has double precision. So I'm assuming that there may be a way for more precision on some machines, but that one can always count on having at least this much.