SAMPLE

SAMPLE NUM1 [FROM NUM2].

SAMPLE randomly samples a proportion of the cases in the active file. Unless it follows TEMPORARY, it permanently removes cases from the active dataset.

The proportion to sample may be expressed as a single number between 0 and 1. If N is the number of currently-selected cases in the active dataset, then SAMPLE K. will select approximately K×N cases.

The proportion to sample can also be specified in the style SAMPLE M FROM N. With this style, cases are selected as follows:

1. If N is the number of currently-selected cases in the active dataset, exactly M cases are selected.

2. If N is greater than the number of currently-selected cases in the active dataset, an equivalent proportion of cases are selected.

3. If N is less than the number of currently-selected cases in the active, exactly M cases are selected from the first N cases in the active dataset.

SAMPLE and SELECT IF are performed in the order specified by the syntax file.

SAMPLE is always performed before N OF CASES, regardless of ordering in the syntax file.

The same values for SAMPLE may result in different samples. To obtain the same sample, use the SET command to set the random number seed to the same value before each SAMPLE. Different samples may still result when the file is processed on systems with different machine types or PSPP versions. By default, the random number seed is based on the system time.