A 窶彝egression line窶 is a graph that represents a best linear approximation to the relation between two data nodes. To see how well this line describes the 窶徨eal窶 relation between the data nodes, you can view the regression line in the same diagram as a scatter plot. If the points are clustered closely around the regression line, the linear approximation is good. You can also compare the regression line to a curve fit. If there is a strong linear relation between the data nodes, then the regression line and the curve fit will be similar. In such cases, you do not gain much by using a more flexible (and thus also more complex) functional relationship as offered by the curve fit.
If the frontmost window is a main document window for a simulation data file, the 窶彝egression line窶 command produces regression lines for all selected pairs of data nodes. To select a pair of data nodes, select the first one whose values should appear along the X-axis in the 窶廡irst selection窶 mode, and the second one whose values should appear along the Y-axis in the 窶彜econd selection窶 mode.
If the frontmost window is an 窶弭Y-plot窶 window created by using the 窶彝egression line窶 command, this menu item is disabled. In this case the window title is of the form:
<node1>(x) <node2>(y).reg
where <node1> is the name of the node whose values appear along the X-axis and <node2> is the name of the node whose values appear along the Y-axis.
If the frontmost window is an 窶弭Y-plot窶 window created by using either the 窶彜catter plot窶 command or the 窶廚urve fit窶 command, this menu item is changed to either 窶廩ide regr. line窶 or 窶彜how regr. line窶 depending on the state of the window. If the plot already contains a regression line, you can use the 窶廩ide regr. line窶 command to hide this regression line. On the other hand, if the plot does not contain a regression line, then you can use the 窶彜how regression line窶 command to show it.
