Other calculation and plotting functionality

Plot any x-y data

This routine allows arbitrary 2-dimensional data points to be plotted as 95% confidence ellipses. To invoke this routine select Plot x-y data option from the task combo box on the main window.

Data point columns should be arranged as:

$x$, $u(x)$, $y$, $u(y)$, $\rho$ (optional))

where ${u}$ denotes uncertainty (at given $\sigma$ level), and $\rho$ denotes correlation coefficient.

If the Data type is set to Tera-Wasserburg, then an equilibrium or disequilibrium concordia curve may also be plotted by setting the activity ratios as for a disequilibrium age calculation, and setting concordia plot options in the Isochron tab of the type-specific plot options window.

If the ‘Data type’ option is set to other x-y, then axis labels may be set in the ‘Axis labels’ dialog that pops up after clicking Ok. For mathematical symbols and expressions, LaTeX syntax can be used (enclosed in dollar symbols). For example, use $^{238}$U for $^{238}\mathrm{U}$ or $\delta^{18}$O for $\delta^{18}$O .

To perform a linear regression, select a regression algorithm from the ‘Fit type’ combo box, or otherwise, select No fit.

Linear regression of any x-y data

To perform linear regression on an arbitrary 2-dimensional dataset, follow the steps above and choose a regression algorithm from the ‘Fit type’ drop-down menu.

Note

If applying a regression algorithm to an arbitrary dataset, be sure that the dataset conforms to the underlying assumptions of the regression algorithm.

Weighted average calculations

To compute a weighted average for arbitrary data points, select Weighted average from the task combo box on the main window, then choose either the Spine or classical algorithms from the ‘Fit type’ combo box. Data point uncertainties may either be specified as:

independent uncertainties on each data point
a covariance matrix that accounts for uncertainties and uncertainty covariances

For the former option, the data selection should contain two columns (the values in the first, and their uncertainties in the second). For the latter option, check the Covariance matrix option under on the main window. The data selection should contain a single column of values to be averaged. After clicking Ok, a dialog will then pop up allowing you to select the n x n covariance matrix data from Excel.