[math] PolynomialSplineFunction.value() domain question

["Litchfield, Ben" <Be...@lpasystems.com>]

(now with a proper subject, in case you confused PolynomialSplineFunction
with commons-logging :) )

The javadocs for this function state that 

"Throws: FunctionEvaluationException - if v is outside of the domain of of
the spline function (less than the smallest knot point or greater than or
equal to the largest knot point)"

I have a series of points, for example ( (12.2,3), (15.4,1.2), (18.9, 4.6)
)  that I need to interpolate some data points from.  The problem is that I
need to be able to interpolate from 12.2 through 18.9 inclusive, right now
an exception is thrown if I try to evaluate for 18.9, which is exactly what
the javadocs state should happen.  Is there a mathematical reason for being
able to evaluate the first datapoint but not the last one?  Can you point me
to a reference if that is the case?  To me it seems to make sense that it
should be able to determine the value at one of the knot points, ".  If this
is an issue in the code then I can submit a patch, just didn't want to waste
my time if it is currently mathematically correct.

Any comments/suggestions would be welcome.

Ben

Re: [math] PolynomialSplineFunction.value() domain question

[Brent Worden <br...@worden.org>]

Ben,

I've looked over some literature and I agree with you that it does not make 
much sense that the function can not be evaluated at one of the knots.

If it is not a bother, could you open a issue at 
http://jakarta.apache.org/commons/math/issue-tracking.html?  Just follow the 
link to Bugzilla.  Also include patch with your changes if you can.  We can 
discuss the changes via Bugzilla once it is entered.

Thanks for your input,

Brent


"Litchfield, Ben" <Be...@lpasystems.com> wrote in message 
news:8766268EF6DFBF4EA7C1C6E58CA0EE9201FE4365@lpa-fs1.lpasystems.com...
(now with a proper subject, in case you confused PolynomialSplineFunction
with commons-logging :) )

The javadocs for this function state that

"Throws: FunctionEvaluationException - if v is outside of the domain of of
the spline function (less than the smallest knot point or greater than or
equal to the largest knot point)"

I have a series of points, for example ( (12.2,3), (15.4,1.2), (18.9, 4.6)
) that I need to interpolate some data points from. The problem is that I
need to be able to interpolate from 12.2 through 18.9 inclusive, right now
an exception is thrown if I try to evaluate for 18.9, which is exactly what
the javadocs state should happen. Is there a mathematical reason for being
able to evaluate the first datapoint but not the last one? Can you point me
to a reference if that is the case? To me it seems to make sense that it
should be able to determine the value at one of the knot points, ". If this
is an issue in the code then I can submit a patch, just didn't want to waste
my time if it is currently mathematically correct.

Any comments/suggestions would be welcome.

Ben




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