This looks like a manifestation of this bug: http://code.google.com/p/sympy/issues/detail?id=2663#c3. It's not clear why it is happening or how to fix it without seeing your definition if QPointF.
Aaron Meurer On Nov 12, 2012, at 1:34 PM, Shriramana Sharma <samj...@gmail.com> wrote: Hello. I'm new to SymPy. I am trying to implement an algorithm in Python for merging Bezier curves from this paper: http://cg.cs.tsinghua.edu.cn/~shimin/pdf/cad%202001_merging.pdf and in it (after spending quite some time in understanding the mathematics, as I am actually a humanities scholar) I have come to the point of implementing the system of linear equations represented by eqn (15). The implementation *seems* quite straightforward: from sympy import Matrix A = zeros ( n + 1 , n + 1 ) # n+1, since we need to iterate 0 to n B = zeros ( n + 1, 1 ) for i in range ( n + 1 ) : # 0 to n B [ i ] = ( DeltaP [ i ] [ n - i ] - ( mu ** i ) * DeltaQ [ i ] [ 0 ] ) * 2 for l in range ( n + 1 ) : # 0 to n A [ i, l ] = ( 1 + ( - mu ) ** ( l + i ) ) * binomCoeff ( l + i, i ) X = A . LUsolve ( B ) (where DeltaP, DeltaQ and binomCoeff are appropriately defined previously in my program). However it seems that I cannot create a Matrix with any arbitrary value type. Since I'm using PyQt for other things I chose QPointF, but that doesn't seem to be permitted since I can't even do: B=Matrix(2,2,[QPointF(1,1),QPointF(2,2),QPointF(3,0),QPointF(4,-1)]) as I get the error: B=Matrix(2,2,[QPointF(1,1),QPointF(2,2),QPointF(3,0),QPointF(4,-1)]) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/dist-packages/sympy/matrices/matrices.py", line 104, in __init__ self.mat = map(lambda i: sympify(i), mat) File "/usr/lib/python2.7/dist-packages/sympy/matrices/matrices.py", line 104, in <lambda> self.mat = map(lambda i: sympify(i), mat) File "/usr/lib/python2.7/dist-packages/sympy/core/sympify.py", line 155, in sympify expr = parse_expr(a, locals or {}, rational, convert_xor) File "/usr/lib/python2.7/dist-packages/sympy/parsing/sympy_parser.py", line 111, in parse_expr expr = eval(code, global_dict, local_dict) # take local objects in preference File "<string>", line 1, in <module> AttributeError: 'Symbol' object has no attribute 'Symbol' I can convert the QPointF to a pair-tuple if that is acceptable, but I am not so sure it's mathematically OK to convert it to a complex pair i.e. x + iy (since the complex multiplication might have side effects when sympy is trying to find the conjugate matrix in the process of find inv(A) ???). Any guidance you people can provide in this regard would be most appreciated. Thank you! -- Shriramana Sharma -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en. -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
