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2018-03-24 08:11:37 +0200 commented question Is there a way to specify the dependent variable in eulers_method?

How is the order of the arguments of f determined from the input expression?

2018-03-23 08:19:49 +0200 received badge  Editor (source)
2018-03-23 08:19:15 +0200 asked a question Is there a way to specify the dependent variable in eulers_method?


sage: u,v = PolynomialRing(QQ,2, "uv").gens()
sage: eulers_method(2*u + v, 1, 5, 0.2, 4)

On the face of it it's ambiguous whether this is solving du/dv = 2*u + v with u(v=1) = 5 or if it's doing dv/du = 2*u + v with v(u=1)=5. In practice it solves the latter, but how is that determined?

It appears to hinge on the order of u and v on the LHS of the first line but I can't find any mention of this in the documentation.

2018-03-21 13:16:37 +0200 asked a question Windows 10: SageMath crashes on start with permission errors, but seems to work if I run "as administrator"

I think I have a workaround, at least, but thought I'd post this in case there's something I can fix or if someone else comes across the same problem, because I couldn't find any mention of these errors myself.

I'm using the Windows installer 0.3 for SageMath 8.1. It appears to install without issues but when I initially opened it I got this sequence of messages:

/etc/profile: line 111: cd: /home/user: Permission denied
WARNING: Failed attempt to cd into /home/user!
mkdir: cannot create directory ‘/home/user/.sagemath-8.1’: Permission denied
cp: cannot create directory '/home/user/.sagemath-8.1': Permission denied
│ SageMath version 8.1, Release Date: 2017-12-07                     │
│ Type "notebook()" for the browser-based notebook interface.        │
│ Type "help()" for help.                                            │
mkdir: cannot create directory ‘/dot_sage’: Permission denied
/opt/sagemath-8.1/local/lib/python2.7/site-packages/IPython/ UserWarning: IPython parent '/dot_sage' is not a writable location, using a temp directory.
  " using a temp directory.".format(parent))

It goes on to say Sage crashed, and asks me to email in the crash report. When I tried opening the shell or Notebook I got similar errors.

Then while groping for something to try I right-clicked and ran "as an administrator" and everything appears to resolve.

I'm not the most savvy at high-level IT stuff but I thought this was strange, as I haven't had to use that feature with anything else I've installed, and there's no shortage of crap I've installed. There's only one account on my computer, there shouldn't be administrator permission issues.