Hello, This is an instance of http://trac.sagemath.org/sage_trac/ticket/847 . I / we haven't had time to fix that one, but hopefully we can get to it tomorrow. For now, you should make sure that f is an actual Python function.
sage: f = lambda x: x sage: Midpoint_Riemann_Sums(0, 5, f, 1000) 12.5250000000000 sage: def f(x): ....: return x ....: sage: Midpoint_Riemann_Sums(0, 5, f, 1000) 12.5250000000000 --Mike On Nov 30, 2007 10:08 AM, David Joyner <[EMAIL PROTECTED]> wrote: > > Again, I don't understand the bug but piecewise seems to work better using > lambda functions. > > sage: f = lambda x: x > sage: fp = Piecewise([[(10,20),f]]) > sage: fp.riemann_sum_integral_approximation(993) > 148900/993 > > Next semester, when I have more time, I plan to revise piecewise. > Maybe I can look into the bug more then... > > > > > On Nov 30, 2007 10:49 AM, john_perry_usm <[EMAIL PROTECTED]> wrote: > > > > Thank you! The following code produces the same error. > > > > f = x > > fp = Piecewise([[(10,20),f]]) > > fp.riemann_sum_integral_approximation(993) > > > > The student is doing this as an assignment for a class on how to write > > programs to solve problems in mathematics. (Newton's Method, Riemann > > sums, Fibonacci numbers, Traveling Salesman, etc.) She's not doing > > this because she needed SAGE to approximate a Riemann sum. They > > started with Maple, and now we're working on SAGE; I'd like to teach > > the class exclusively in SAGE one day. > > > > regards > > john perry > > > > On Nov 30, 9:00 am, "David Joyner" <[EMAIL PROTECTED]> wrote: > > > I'm not sure what the cause of the error is but, FYI, some Riemann sum > > > stuff is > > > already implemented in piecewise.py. > > > > > > > > On Nov 30, 2007 9:41 AM, john_perry_usm <[EMAIL PROTECTED]> wrote: > > > > > > > > > > > > > Hi, > > > > > > > One of my students was writing a procedure to implement a Midpoint > > > > Riemann Sum in SAGE. The procedure that she devised is given below, > > > > and it looks reasonable enough to me. Unfortunately it generates a > > > > SAGE exception (AttributeError, line 2051 of calculus.py) under > > > > certain bizarre circumstances; try for example a=10,b=20,f=x,n=991 > > > > (which works fine) then n=992 with the same a,b,f. > > > > > > > Any assistance would be appreciated. Maybe I don't know Python well > > > > enough? :-) I have verified the exception using both SAGE-2.8.7 on > > > > Fedora Core 7 and SAGE-2.8.13 on Windows. > > > > > > > regards > > > > john perry > > > > > > > Her procedure: > > > > > > > def Midpoint_Riemann_Sums(a,b,f,n): > > > > delta_x = (b-a)/(n*1.0) > > > > result = 0 > > > > for i in range(1, n+1): > > > > xi = ((delta_x/2)+a)+(i*delta_x) > > > > result = result+f(xi)*delta_x > > > > return result > > > > > > > The error message: > > > > > > > Traceback (most recent call last): > > > > File "/atlas/perry/sage_notebook/worksheets/apetrinec55/1/code/ > > > > 71.py", line 4, in <module> > > > > exec > > > > compile(ur'Midpoint_Riemann_Sums(Integer(10),Integer(20),f,Integer(1000))' > > > > + '\n', '', 'single') > > > > File "/usr/local/sage-2.8.7-fedora_core_7-i686-Linux/data/extcode/ > > > > sage/", line 1, in <module> > > > > > > > File "sage_object.pyx", line 87, in sage_object.SageObject.__repr__ > > > > File "/usr/local/sage-2.8.7-fedora_core_7-i686-Linux/local/lib/ > > > > python2.5/site-packages/sage/calculus/calculus.py", line 2896, in > > > > _repr_ > > > > return self.simplify()._repr_(simplify=False) > > > > File "/usr/local/sage-2.8.7-fedora_core_7-i686-Linux/local/lib/ > > > > python2.5/site-packages/sage/calculus/calculus.py", line 2051, in > > > > simplify > > > > S = > > > > evaled_symbolic_expression_from_maxima_string(self._maxima_init_()) > > > > File "/usr/local/sage-2.8.7-fedora_core_7-i686-Linux/local/lib/ > > > > python2.5/site-packages/sage/calculus/calculus.py", line 3044, in > > > > _maxima_init_ > > > > return '(%s) %s (%s)' % (ops[0]._maxima_init_(), > > > > > > > ...and then several hundred more of that last line. > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://sage.math.washington.edu/sage/ and http://sage.scipy.org/sage/ -~----------~----~----~----~------~----~------~--~---
