Re: ListInterpolation

• To: mathgroup at smc.vnet.net
• Subject: [mg58342] Re: ListInterpolation
• From: "Valeri Astanoff" <astanoff at yahoo.fr>
• Date: Tue, 28 Jun 2005 21:56:41 -0400 (EDT)
• References: <d9r4tv\$55q\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Stephane,

In your example, seems to me that if there are
4 occcurrences of x and 2 of y, then the data
should be a {4,2} list (which is not the case,
so your data have to be transposed).

If I was you, in such a case of explicit values
of the variables, I would first "regularize"
the data to get an evenly spaced grid, before
using ListInterpolation.

An example of what you could do :

In[1]:=data1={{1, 1.3, 2.5, 5},{1, 2, 3, 4}}//Transpose

Out[1]={{1,1},{1.3,2},{2.5,3},{5,4}}

In[2]:=data2={{1, 1.3, 2.5, 5},{5, 6, 7, 8}}//Transpose

Out[2]={{1,5},{1.3,6},{2.5,7},{5,8}}

In[3]:=f1=Interpolation[data1];

In[4]:=f2=Interpolation[data2];

In[5]:=gridData={Table[f1[x],{x,1,5,4/3}],
Table[f2[x],{x,1,5,4/3}]}//Transpose

Out[5]={{1.,5.},{3.05919,7.05919},{2.22269,6.22269},{4.,8.}}

In[6]:=res = ListInterpolation[gridData, {{1, 5}, {0.5, 1.3}}] ;

>From In[6]:=
ListInterpolation::inhr:Requested order is too high; order has been
reduced to {3, 1}

In[7]:=res[1,0.5]

Out[7]=1.

In[8]:=res[5,1.3]

Out[8]=8.

In[9]:=res[2,1.1]

Out[9]=6.03108

Valeri

```

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