Re: ListInterpolation

*To*: mathgroup at smc.vnet.net*Subject*: [mg58423] Re: ListInterpolation*From*: dh <dh at metrohm.ch>*Date*: Sat, 2 Jul 2005 04:06:21 -0400 (EDT)*References*: <d9r4tv$55q$1@smc.vnet.net> <200506290157.VAA15270@smc.vnet.net> <da0b8t$fiu$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi Stéphane, what you have in mind is LINEAR interpolation. This can be done giving the option InterpolationOrder ->1. Then you get 5/3. However, if the interpolation order is higher, points farther away will have an effect. To guard against unexpected surprises, it is generally safe to use a low interpolation order. sincerely, Daniel Stéphane Fay wrote: > Thank you for your answer, but when I try > > res = ListInterpolation[ > Transpose[{{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10 , 11 , 12}}], > {{1, 1.3, 2, 5}, {0, 1.5, 2}}]; > > I get > > res[1, 0.5] = 1. > > whereas for me the correct answer would be res[1, 0.5] = 5/3 > > since {1, 1.3, 2, 5} is the x coordinate of the data table {{1, 2, 3, > 4}, {5, 6, 7, 8}, {9, 10 , 11 , 12}} and {0, 1.5, 2} the y > coordinates. Where does I make a mistake? > > > On 6/29/05, Peter Pein <petsie at dordos.net> wrote: > >>St=E9phane Fay schrieb: >> >>>Dear everyone, >>> >>>I have a problem with the ListInterpolation instruction. I would like >>>to specify some explicit lists of positions for grid lines like this: >>> >>>res == ListInterpolation[{{1, 2, 3, 4}, {5, 6, 7, 8}}, {{1, 1.3, 2. 5, >>>5}, {0.5, 1.3}}] >>> >>>But it does not work: when I try to calculate res[2, 1.1], I get >>>ListInterpolation[{{1, 2, 3, 4}, {5, 6, 7, 8}}, {{1, 1.3, 2.5, 5}, >>>{0.5, 1.3}}][2, 1.1] >>> >>>I thank you in advance for your help. >>> >>>Yours sincerely >>> >>> Stephane Fay >>> Paris Observatory >>> France >>> >> >>Your input is not in proper format (and use "=" for assignments, not "=="): >> >>In[1]:= res = ListInterpolation[ >> Transpose[{{1, 2, 3, 4}, {5, 6, 7, 8}}], >> {{1, 1.3, 2.5, 5}, {0.5, 1.3}}]; >>From In[1]:= >>ListInterpolation::inhr: >>Requested order is too high; order has been reduced to {3, 1}. More... >> >>In[2]:= res[2, 1.1] >>Out[2]= >> 6.031081081081081 >>-- >>Peter Pein >>Berlin >> >> > >