Use a XY Scatter chart rather than a line chart. Though they look
similar, only the former supports numerical values on the x-axis.

From just plotting the data, it would appear that a linear fit would be
the most appropriate. You should use LINEST with the Stats option to
see if your results are significant. See Trendline coefficients
(http://www.tushar-mehta.com/excel/ti...efficients.htm).

--
Regards,

Tushar Mehta
www.tushar-mehta.com
Multi-disciplinary business expertise
+ Technology skills
= Optimal solution to your business problem
Recipient Microsoft MVP award 2000-2005

In article <[email protected]>,
[email protected] says...
> I'm trying to fit a 3rd degree trend line to a data series with independent
> values starting from -8 to 10. The 3rd degree equation that I get keeps
> assuming that the first independent data point is zero, and so, the
> y-intercept of the equation is not the value for -8. These are the data
> points,
>
> m Freq (cm-1)
> -8 2107
> -7 2112
> -6 2116
> -5 2120
> -4 2124
> -3 2128
> -2 2132
> -1 2136
> 0 2139
> 1 2147
> 2 2151
> 3 2155
> 4 2158
> 5 2162
> 6 2166
> 7 2169
> 8 2173
> 9 2176
> 10 2180
> And so, the y-intercept at x=0 should be close to 2139 instead of the 2104
> value that I get. How to make excel recognize that the first data point is
> not zero?
> Please help,
> Juan
>
>