es can be relied upon to exist (barring changes in Gri
itself), unless you `<font color="#82140F"><code>delete</code></font>' them.
<li>
<b>Spontaneous</b> variables (which are created by certain Gri commands,
and only exist if these commands have been executed).  For example, the
`<font color="#82140F"><code>regress</code></font>' command defines `<font color="#82140F"><code>..coeff0..</code></font>' (the intercept of the
fitted line), `<font color="#82140F"><code>..coeff1..</code></font>' (the slope of th