Re: import data problem
- To: mathgroup at smc.vnet.net
- Subject: [mg123253] Re: import data problem
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Tue, 29 Nov 2011 07:04:51 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
On 11/28/11 at 5:54 AM, hvdosten at gmail.com (Harry) wrote:
>I don't understad what happens with my data...
>
>There are 401 lines of input data). The last lines are:
>...
>19.7999992 -9.13599968 19.8500004 -11.6960001 19.8999996 -11.9519997
>19.9500008 -12.2080002 20. -12.9759998
>Importing these data in Mathematica via
>data = Import["00000.dat", "Table"]
>and everything seems to be ok. But if I try this:
>y = LinearModelFit[data, {x, x^2}, x]
>there is the error message: LinearModelFit::ivar: "{20.05} is not a
>valid variable"
This error indicates you have assigned a value to x
(specifically {20.05}). So, Mathematica evaluates
LinearFit[data, {x, x^2}, x] as
LinearFit[data, {{20.05}, {402.0025}}, {20.05}] which causes the
error. To fix this do one of the following
Clear[x];
y = LinearModelFit[data, {x, x^2}, x]
Block[{x},y = LinearModelFit[data, {x, x^2}, x]]
or start over with a fresh session.