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.