Hi,
On Jun 25, 9:12 pm, David Joyner <wdjoy...@gmail.com> wrote:
> I know multiplication is very finicky. You might try using
> R.<t> = PolynomialRing(RR, "t") instead, but I'm not sure that will work
> either.
>
> Can you post more of your code so I can give a more detailed answer?
a = [-1, 0, 1.5, 3.2, 5]
k = len(a)
t = var('t')
def delta(c,d):
if c == d:
return 1
else:
return 0
def w(j,k,t):
return (t-a[j-1])/(a[j+k-2]-a[j-1])
# for j,k integers it is just an expression in t
L1 = []
for j in [1..k-1]:
L1.append( piecewise([[(a[i-1],a[i]),delta(i,j)] for i in
[1..k-1]]) )
L2 = []
for j in [1..k-2]:
L2.append( w(j,2,t)*L1[j]+(1-w(j+1,2,t))*L1[j+1] )
Traceback (click to the left for traceback)
...
TypeError: unsupported operand parent(s) for '*': 'Symbolic Ring' and
'<type 'instance'>'
w(1,2,t)*L1[1]
Traceback (click to the left for traceback)
...
TypeError: unsupported operand parent(s) for '*': 'Symbolic Ring' and
'<type 'instance'>'
L1[1]; type(L1[1])
Piecewise defined function with 4 parts, [[(-1, 0), 0], [(0,
1.50000000000000), 1], [(1.50000000000000, 3.20000000000000), 0],
[(3.20000000000000, 5), 0]]
<type 'instance'>
w(1,2,t); type(w(1,2,t))
t + 1
<type 'sage.symbolic.expression.Expression'>
I am guessing that having them both as functions of a variable "t" I
should be able to manipulate them (it seems piecewise is not a
function). Assuming, that is, that things like the "1" in the
definition of L2 above would be coerced accordingly.
David
> On Thu, Jun 25, 2009 at 2:17 PM, David Sevilla<sevil...@gmail.com> wrote:
>
> > Hi,
>
> > I am trying to construct the usual spline basis functions. In short, I
> > start with several piecewise functions that take values 1 and 0 only,
> > and then make combinations of them. But there is something with the
> > syntax that I am not managing to do well, I suppose:
>
> > L[1]
> > Piecewise defined function with 3 parts, [[(-1, 0), 0], [(0,
> > 1.50000000000000), 0], [(1.50000000000000, 3.20000000000000), 1]]
>
> > t = var('t')
> > L[1]*t
> > Traceback (click to the left for traceback)
> > ...
> > AttributeError: 'sage.symbolic.expression.Expression' object has no
> > attribute 'domain'
>
> > It seems to me that I have to set things up so that L[1] is a function
> > of t as well. I tried "lambda t: " in front where I define it, but now
> > L[1] is a function whose value is always a certain piecewise
> > function :)
>
> > Any suggestions?
>
> > Thanks,
>
> > David
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