[sage-support] Re: sage notebook worksheets lost content

[bsdz]

Thanks for the suggestion. Unfortunately, it looks like all my
workbooks were somehow trashed some time between the 25th and 29th of
May this year. I might take a look through this newsgroup to see if
it's a known issue. I guess I might have to accept that I lost all my
work.

On 18 Aug, 15:47, Marshall Hampton hampto...@gmail.com wrote:
 There might be a better way to do this, but here is one way:

 In a cell of your worksheet, do:

 %sh
 ls -t ../../snapshots |head

 which will give you a list of the most recent snapshots of your
 worksheets.  For my worksheet, the most recent one was called:
 1250606636.bz2.  So then you can do:

 %sh
 cp ../../snapshots/1250606636.bz2 .

 and you will get a link to that compressed worksheet snapshot.  You
 could then unpack it, and then paste it in after clicking Edit in
 the notebook.

 That's a little tedious if you have lots of worksheets lost in this
 way - it might be possible to restore all of them with a script, but
 I'm not sure exactly how to do that on sagenb.org.

 -Marshall Hampton

 On Aug 18, 9:26 am, bsdz blai...@googlemail.com wrote:

  Hi

  I just checked back at my workbooks onwww.sagenb.organdfound most
  of my workbooks have had their content replaced with a single e
  character.

  Does anyone know how I can recover my workbooks?

  Blair
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[sage-support] sage notebook worksheets lost content

[bsdz]

Hi

I just checked back at my workbooks on www.sagenb.org and found most
of my workbooks have had their content replaced with a single e
character.

Does anyone know how I can recover my workbooks?

Blair
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[sage-support] faster alternative to using maxima's part function

[bsdz]

Hi,

Is anyone aware of an alternative to maxima's part function.

http://maxima.sourceforge.net/docs/manual/en/maxima_6.html#IDX182

It allows one to access any part of an algebraic expression using
various indexes. A list of indexes uniquely defines any part of an
expression such as a sum part or exponent.

I ask because a while back I implemented a useful function but felt it
was too slow because it had to constantly send requests to maxima's
lisp interpreter.

Thanks
Blair
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[sage-support] Re: Error on sagenb.org on log in.

[bsdz]

I had the same problem. A workaround is to click the jsMath button in
the bottom right hand corner of your notebook and choose Options, then
set Use native Unicode fonts radio button.

On Feb 2, 1:34 pm, Kevin Loranger kevinloran...@gmail.com wrote:
 After I log into SAENB:
 It looks like jsMath failed to set up properly (error code -7).  I will try
 to keep going, but it could get ugly.
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[sage-support] Convert a SymbolicEquation into a MaximaElement

[bsdz]

Hi,

Is it possible to convert a SymbolicEquation into a MaximaElement
easily? The opposite to: -

maxima('x^2 + y^2 = 0').sage()

Something like this: -

x, y = var('x y')
b = x^2 + y^2 == 0
b.maxima()

I would like to do some manipulations on an equation by breaking it
down into terms and parts.

Thanks
Blair


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[sage-support] Re: How to replace variables in function?

[bsdz]

(Sorry if this reply appears twice - 1st one disappeared?)

This worked for me: -

H, p, Pole1, Pole2, Pole3, Ts, z, f = var(H p Pole1 Pole2 Pole3 Ts z
f)
p = (2/Ts)*(z-1)/(z+1)
z = exp(I*2*pi*Ts*f)
H = (p^3)/((p-Pole1)*(p-Pole2)*(p-Pole3))
show(H)

The only difference is that I have declared the variables in the first
line. Hope that helps.

On Dec 8, 5:58 pm, Sand Wraith [EMAIL PROTECTED] wrote:
 Hi all! Please help me to replace variables:

 I have this function:

 H(p)=(p^3)/((p-Pole1)*(p-Pole2)*(p-Pole3))

 where Pole1,Pole2,Pole3 - complex:

 r=2*2*pi
 Pole1=r*exp(I*2*pi/3)
 Pole2=-r
 Pole3=r*exp(-I*2*pi/3)
 Ts=0.1

 And I need to make a few replaces:

 need to replace p with (2/Ts)*(z-1)/(z+1), where z is a new
 variable, and then replace z with exp(I*2*pi*Ts*f). To have H(f)
 function at the end.

 I am trying to write:

 z=exp(I*2*pi*Ts*f)
 p=(2/Ts)*(z-1)/(z+1)
 H=(p^3)/((p-Pole1)*(p-Pole2)*(p-Pole3))

 and now if I want to look at H:
 H
 or
 show(H)
 I've got many errors...

 tail of long output:

 sage-display
 stdin:16:Incorrect syntax: Syntax error
 _tmp_ : (8000.0(
               ^
 sage-display(%o90)

 what is wrong with it?

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[sage-support] Change of variable in Differential Equation

[bsdz]

Hi

I was wondering if it is possible in Sage (perhaps even Maxima) to
change the variable in an ODE or PDE algebraically. I have set up a
simple PDE with the following: -

x, t, k_1, k_2 = var(x t k_1 k_2)
y = function('y', x, t)
PDE = lambda f : k_1 * x^2 * diff(f,x,2) + diff(f,t) + k_2*(x*diff
(f,x)-f)
PDE(y(x,t))

I would like to how to make the change of variable x = exp(z) where z
is real. Is this possible?

Thanks in advance
Blair
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