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Option
is the PROC FASTCLUS option,
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x
is the first numeric or character value(s) or condition(s) that modifies the option,
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y
represents one or more subsequent numeric or character value(s) or condition(s) that modifies the option, and
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the
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character is used to delimit individual conditions.
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This option specifies the number of
bins
used in the bin-sort algorithm for computing
medians
for
LEAST=1
. By default, PROC FASTCLUS uses from 10 to 100 bins, depending on the amount of memory available. Larger values use more memory and make each iteration somewhat slower, but they can reduce the number of iterations. Smaller values have the opposite effect. The minimum value of
n
is 5.
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This option specifies the convergence criterion. Any nonnegative value is permitted. The default value is 0.0001 for all values of
p
if LEAST=
p
is explicitly specified. Otherwise, the default value is 0.02. Iterations stop when the maximum relative change in the cluster seeds is less than or equal to the convergence criterion and additional conditions on the homotopy parameter, if any, are satisfied. (See the
HP=
option.) The relative change in a cluster seed is the distance between the old seed and the new seed divided by a scaling
factor
. If you do not specify the
LEAST=
option, the scaling factor is the minimum distance between the initial seeds. If you specify the
LEAST=
option, the scaling factor is an
L
1
scale estimate and is recomputed on each iteration. Specify the
CONVERGE=
option only if you specify a
MAXITER=
value greater than 1.
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This option deletes cluster seeds to which
n
or fewer
observations
are assigned. Deletion occurs after processing for the
DRIFT
option is completed and after each iteration specified by the
MAXITER=
option. Cluster seeds are not deleted after the final assignment of observations to clusters, so in rare cases a final cluster might not have more than members. The
DELETE=
option is ineffective if you specify
MAXITER=0
and do not specify the
DRIFT
option. By default, no cluster seeds are deleted.
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After initial seed selection, each observation is assigned to the cluster with the nearest seed. After an observation is processed, the seed of the cluster to which it is assigned is recalculated as the
mean
of the observations currently assigned to the cluster. Thus, the cluster seeds drift about rather than remaining fixed for the duration of the pass.
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This option specifies the criterion for updating the homotopy parameter. The homotopy parameter is updated when the maximum relative change in the cluster seeds is less than or equal to
c
. The default is the minimum of 0.01 and 100 times the value of the
CONVERGE=
option.
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HP=p
1
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This option specifies
p
1
as the initial value of the homotopy parameter. The default is 0.05 if the modified Ekblom-Newton method is used. Otherwise, it is 0.25.
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This option requests
imputation
of
missing values
after the final assignment of observations to clusters. If an observation that is assigned (or would have been assigned) to a cluster has a missing value for
variables
used in the cluster analysis, the missing value is replaced by the corresponding value in the cluster seed to which the observation is assigned (or would have been assigned). If the observation cannot be assigned to a cluster, missing value replacement depends on whether the
NOMISS
option is specified. If
NOMISS
is not specified, missing values are replaced by the mean of all observations in the
DATA=
data set having a value for that variable. If
NOMISS
is specified, missing values are replaced by the mean of only observations used in the analysis. (A weighted mean is used if a variable is specified in the
WEIGHT
statement.) For information about cluster assignment see the section OUT= Data Set. If you specify the
IMPUTE
option, the imputed values are not used in computing cluster statistics.
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This option causes PROC FASTCLUS to use an iteratively reweighted least squares method instead of the modified Ekblom-Newton method. If you specify the IRLS option, you must also specify
LEAST=
, where
1 <
p
< 2
. Use the IRLS option only if you encounter convergence problems with the default method.
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This option excludes observations with missing values from the analysis. However, if you also specify the
IMPUTE
option, observations with missing values are included in the final cluster assignments.
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This option specifies an input data set from which initial cluster seeds are to be selected. If you do not specify the
SEED=
option, initial seeds are selected from the DATA= data set. The
SEED=
data set must contain the same variables that are used in the data analysis.
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This option prevents an observation from being assigned to a cluster if its distance to the nearest cluster seed exceeds the value of the
STRICT=
option. If you specify the
STRICT=
option without a numeric value, you must also specify the
RADIUS=
option, and its value is used instead. In the
OUT=
data set, observations that are not assigned due to the
STRICT=
option are given a negative cluster number, the absolute value of which indicates the cluster with the nearest seed.
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Type specific PROC FASTCLUS options in the
PROC FASTCLUS Options
field.
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Refer to the
PROC FASTCLUS documentation
for more information.