how to find root of a spline

asked 2012-09-18 04:41:52 +0100

wizulis
13 ●1 ●2 ●5

Basicaly the title says it: I have data points for which i need to find the x value where y is a known value. I tried it like this, but it seems that it should be done differently:

from sage.gsl.all import spline
data=[[0,1],[1,2],[2,2.2],[3,2.4],[4,0.4],[5,0.1],[6,-0.5]]
func=spline(data)
x=var('x')
find_root(func(x),0,6)
..[Error message with main idea - TypeError: unable to simplify to float approximation]

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answered 2012-09-18 05:48:58 +0100

achrzesz
2768 ●5 ●25 ●60

sage: find_root(func,0,6)   
5.3157137464283455
sage: plot(func,[x,0,6])

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Just to elaborate, when you did `func(x)`, you wanted Sage to evaluate the spline at the symbolic variable `x`. But our splines aren't (yet) symbolic, so it raised an error because it wanted an actual numeric input.

kcrisman ( 2012-09-18 09:27:06 +0100 )edit

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Asked: 2012-09-18 04:41:52 +0100

Seen: 554 times

Last updated: Sep 18 '12

how to find root of a spline edit