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DATA>
In each of the data formats, the data can be put on as many lines as needed but each line
must not exceed 80 characters. Values on a line must be separated with commas or one or more
spaces. Notice that a semi-colon separates different types of input data when both grouped and
ungrouped data formats are used for clustered populations and specifies the end of data input for
the sample. Unlike commands, information entered beyond the semi-colon will create an error. The
following example for format 1 would not be valid because distances are grouped and cluster sizes
ungrouped:
n1,n2,n3; s1,s2,s3,...,sn;
Instead, the grouped data (frequencies) and ungrouped data (cluster sizes) must start on a separate
line as shown in Table 1.
If there are no observations for a SAMPLE, data values are not given, but the semicolons must
still be entered to indicate a sample of size 0. For formats 1 and 4, two semicolons must be given on
separate lines and for formats 2, 3 and 5, only one semi-colon is required.
If the observed objects are clusters, we recommend that you do not use format 1 and 4 in
Table 1. Instead, we recommend that the measurements (distance and cluster size) be entered
ungrouped (EXACT) (formats 2 or 5), even if they were recorded in intervals (grouped). Use the
interval midpoint as the distance measurement for each observation in an interval. This enables
a more detailed analysis because the distance and cluster size measurements are paired for each
object. For instance, if a WIDTH is chosen which truncates some of the distance observations, it is
not possible to discard the appropriate cluster sizes unless the measurements are paired as they are
in ungrouped data entry. Likewise, if you wish to use cluster sizes which were observed within a
pre-specified distance or perform a size-bias regression, this can only be done if distances and cluster
size measurements are entered in pairs. Proper estimation with the true interval nature of the
distance data is obtained by specifying INTERVALS with the DISTANCE command at the ESTIMATE
prompt (pg:110-111,149-150). This also allows one or more intervals to be combined into larger
intervals in the analysis. A simple example with "unrealistically" small numbers of observations and
intervals is given below to show how interval distance data are entered as exact using the midpoint
and then analyzed using the intervals in which they were collected:
OPTIONS;
DIST=PERP;
<-- exact is assumed
OBJECT=CLUSTER;
END;
DATA;
SAMPLE/EFFORT=14.5;
.5 2 .5 4 .5 1 1.5 6 1.5 2 2.5 7;
SAMPLE/EFFORT=4.5;
.5 1 1.5 4 2.5 2 2.5 6;
END;
ESTIMATE;
DIST/INTERVALS=0,1,2,3; <-- data originally collected in these intervals
ESTIMATE/KEY=HN /ADJUST=POLY;
END;
The commands, which are valid at the
order.
DATA> prompt, are described below in alphabetical
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