Vernier Spectro Pro - Manual (Page 46)

Spectro Pro Reference
48 Spectro Pro
The graph portion of this window gives you a preview of the fit and
allows the selection region to be modified. To perform a curve fit,
choose first the type of fit from the scrolling list at lower left. For the
case of the polynomial fit, enter the degree of the polynomial in the
Degree field. Next, choose the column to be approximated by the fitted
equation. Click on Try Fit to see the result. Modify your choices as
desired. You can modify your data selection by repeating a drag across a
portion of the data and clicking on Try Fit again. Once you like the fit,
Click on OK to place the fit on the main graph window, or Cancel to
discard the fit altogether.
Clicking Create Column will place a new column in the data table
containing the value of the fitted equation at each time.
The Curve Fit Options tab holds a new dialog box.
The Curve Fit Options tab allows you to determine which fit statistics
are displayed on the graph. The Equation’s Coefficients are the fitted
parameters. The Mean Square Error and its square root, the Root Mean
Square Error, measure how far away on average the fitted function is
from the data. The Root Mean Square Error is in the units of the data on
the y-axis.
You can also specify the style and color of the line representing the fit.
The Sample Line region provides a preview of the line appearance.
The Displayed Precision field allows you to set the number of displayed
digits in the curve fit floating boxes. Select one of Decimal Places (a
fixed number of places past the decimal point) or Significant Figures
(the number of digits displayed, plus any need to show magnitude).
Enter the desired numerical setting for either mode.
For the linear fit only, the fit and its statistics are determined as follows.
We have N ordered pairs of x
i
and y
i
. The best fitting line y = ax + b is
then given by