SAMPLE num1 [FROM num2].
SAMPLE randomly samples a proportion of the cases in the active file. Unless it follows TEMPORARY, it operates as a transformation, permanently removing cases from the active file.
The proportion to sample can be expressed as a single number between 0
and 1. If
k is the number specified, and
N is the number
of currently-selected cases in the active file, then after
k*N cases will be
The proportion to sample can also be specified in the style
FROM N. With this style, cases are selected as follows:
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 (see N OF CASES).
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
differing endianness or floating-point formats. By default, the
random number seed is based on the system time.