Sachin, I like where you are going with this. If I'm interpreting it correctly, each CoordinateSystem has to be attached to a ReferenceFrame, and is fixed (although possibly rotated and/or translated upon coordinate system definition) with respect to that ReferenceFrame? Prasoon, Stefan, others - what are your thoughts on this?
I think there might be some better/easier ways to access basis vectors and some other issues, but that discussion can come after a consensus is reached on the CoordinateSystem/ReferenceFrame distinctions. -Gilbert On Wed, Jun 5, 2013 at 12:21 AM, Sachin Joglekar <srjoglekar...@gmail.com>wrote: > @Stefan : I would recommend having a separate class for ScalarFields. Even > I wasn't sure of the need for this till yesterday, when we came across the > problem of how the user would define a scalar field in any coordinate > system he wants(which is not the global frame). In such cases, I propose > something like the following- > rho = ScalarField(6*x**2*y, c_rect1) > rho.express(c_sph) > > If we find a better way to this this I am all for it, but for now the > above seems elegant and convenient. > > In any case, I tried my hand at expressing a few of the steps put forward > by Stefan in a mock SymPy session. I would request all of you to have a > look at it and express your views (please elaborate on the reasons for any > editing if done in the current code). It is a WIP obviously. > The wiki link - https://github.com/sympy/sympy/wiki/Vectors-EM-framework > > > > > On Wed, Jun 5, 2013 at 4:16 AM, Stefan Krastanov < > krastanov.ste...@gmail.com> wrote: > >> Here is a quick summary from today: >> >> - probably scalar fields will be represented simply by SymPy expressions >> where some of the symbols will have special meaning (the coordinates) >> - probably vectors will be represented like in mechanics (one object, not >> necessarily a sympy expression) >> >> - using reference systems translated and rotated with respect to each >> other is rather unclear at the moment: before continuing with the irc >> meetings I would suggest that the students provide a _nice_ wiki presenting >> the answers to the questions in the previous thread and also the following >> questions: >> >> Bellow is the question in "mathematical" terms. Transform it in whatever >> way you find appropriate to fit your suggested APIs: >> >> - in 3D >> - I have three points A, B and C. >> - I use each of them as the zero of three different coordinate systems >> - The A and B systems are both Cartesian but rotated by theta_AB around >> axis_AB >> - The C system is spherical (r, phi, theta). The theta=0 axis is rotated >> wrt the z axis of A by the Euler angles alpha, beta, gamma >> - I define a scalar field in A, another scalar field in B and a vector >> field in C >> - I want the sum of the scalar fields >> - I want the gradient of that sum >> - I want the convective derivative of the vector field from C wrt the >> gradient from the question above >> - I want to express the entities from the above 4 question in each of the >> three coordinate systems. >> - For all this please explicitly choose some fields for the examples and >> calculate the expected results by hand (and add them to the example session >> as mock results). >> >> I think that this will really stress test the suggested API. The only >> thing missing is the time dependence needed in mechanics. I strongly >> suggest that we first finish the considerations above before continuing. >> >> @Prasoon and Sachin, when will you be able to provide a detailed wiki >> page with an example session for what is asked here? There is really no >> need to hurry (officially GSoC has not started yet) so please take your >> time (a week?). >> >> Stefan >> >> >> On 4 June 2013 01:12, Aaron Meurer <asmeu...@gmail.com> wrote: >> >>> The discussion was at http://piratepad.net/KBviCWUlA3. >>> >>> I'm curious what you think of this kind of discussion, as opposed to >>> IRC. Google docs is also an option (it has a chat). I think the >>> downside is that unlike IRC, which is logged at >>> http://colabti.org/irclogger/irclogger_logs/sympy, it's a little >>> harder to search through these discussions afterwords. >>> >>> Aaron Meurer >>> >>> >>> On Mon, Jun 3, 2013 at 4:16 PM, Stefan Krastanov >>> <krastanov.ste...@gmail.com> wrote: >>> > Today we had the first discussion with Prasoon and Sachin about their >>> > projects. >>> > >>> > We did not progress much but at least we outlined the two general >>> approaches >>> > that we can use for these modules (specifically for creating vector >>> fields). >>> > I will give them somewhat arbitrary names here: >>> > >>> > - the `mechanics` way - having a Vector class that keeps all the >>> information >>> > about the field and it is not part of expression trees in the way >>> Basic and >>> > Expr are. For instance Vector(something along >>> cartesian.x)+Vector(something >>> > along spherical.r) will result in Vector(complex internal structure). >>> > >>> > - the `diffgeom` way - having base/unit vectors and building all the >>> rest in >>> > terms of their linear combinations (all this expressed as sympy >>> > expressions). >>> > >>> > >>> > >>> > Prasoon and Sachin did not have the time to look at the example >>> problem that >>> > was given in the previous email yet (no harm done there, there is >>> still some >>> > time before the official starting date). Probably this will be the >>> subject >>> > of our next discussion. >>> > >>> > The next discussion was scheduled for tomorrow. After that I suggest >>> that we >>> > keep most of the discussions to the mailing list and the gihub wiki >>> and meet >>> > on irc / realtime wikis / google docs / etc once a week. >>> > >>> > Stefan >>> > >>> > -- >>> > You received this message because you are subscribed to the Google >>> Groups >>> > "sympy" group. >>> > To unsubscribe from this group and stop receiving emails from it, send >>> an >>> > email to sympy+unsubscr...@googlegroups.com. >>> > To post to this group, send email to sympy@googlegroups.com. >>> > Visit this group at http://groups.google.com/group/sympy?hl=en-US. >>> > For more options, visit https://groups.google.com/groups/opt_out. >>> > >>> > >>> >>> -- >>> You received this message because you are subscribed to the Google >>> Groups "sympy" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to sympy+unsubscr...@googlegroups.com. >>> To post to this group, send email to sympy@googlegroups.com. >>> Visit this group at http://groups.google.com/group/sympy?hl=en-US. >>> For more options, visit https://groups.google.com/groups/opt_out. >>> >>> >>> >> > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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