Interpolation difficulty

*To*: mathgroup at smc.vnet.net*Subject*: [mg116547] Interpolation difficulty*From*: Javier <mathquestion0 at gmail.com>*Date*: Sat, 19 Feb 2011 05:13:22 -0500 (EST)

Interpolation[{{2, 1}, {4, 5}, {5, 2}}, InterpolationOrder -> 0] gives a function which is 5 from 2 to 4, and 2 from 4 to 5. I want as a result a function which is 1 from 2 up to 4, then 5 from 4 up to 5. It should extrapolate to x=1 giving also 1, and to x=6 giving 2. Is this possible? Many thanks in advance.