General purpose variables

As well as the values in the data table, EASISTAT provides a number of other variables which are not needed for the standard statistical tests but which may be used for a variety of other purposes and are particularly useful for general mathematical manipulations. Firstly, there are twenty general purpose variables which can be set to any values and used in arithmetic and logical expressions. These variables are referred to as V1, V2...V20, but they can also be labelled like the data columns and then referred to by these labels. The values are set by the DERIVE command and the labels are set by the LABEL command. For example if one wishes to have a value for pi available in expressions one could enter:

LABEL V1 PI
DERIVE PI ARCCOS(-1)

This would set the label of first general purpose variable to be pi, and then set its value to be the arccos of -1 in radians. It could thereafter be referred to in expressions as pi, e.g.:

C2+PI*C3

These variables can be displayed with the command:

LIST VARIABLES

which can be shortened to:

L V

There are three special variables which are set by the SUMMARY command, and these are referred to as XNUMBER, XTOTAL and XMEAN. When the SUMMARY command is carried out, XNUMBER is set to the number of items present (valid rows used), XTOTAL is set to the total of the values used and XMEAN is set to the mean of the values (which would be XTOTAL/XNUMBER). The purpose of these variables is to make possible the construction of other statistical tests which may not be directly built in to EASISTAT. The values obtained from the SUMMARY command can be used in subsequent arithmetic expressions. An example of this is given in the section on the INPUT command.

As an extension to this there are another twenty variables which are set by the SUMMARY command and other statistical commands. These are referred to as VV1, VV2...VV20. How these are set for each command can be discovered by displaying them after the command is performed. They are displayed by the command:

LIST VV

So if for example one wishes to use the value of the standard error of the mean as calculated by the SUMMARY command one could enter the following:

SUMMARY C5
LIST VV

It then becomes clear that VV7 has been set to the standard error. If one wished to make a permanent copy of it one could then set one of the first twenty variables to have that value, since the value of VV7 itself will be changed by the next statistics command which is performed:

DERIVE V1 VV7