UCHART Statement: ANOM Procedure

Input Data Sets

DATA= Data Set

You can read response counts for groups from a DATA= data set specified in the PROC ANOM statement. Each response specified in the UCHART statement must be a SAS variable in the data set. This variable provides the count (number of occurrences) for groups indexed by the group-variable. The group-variable, specified in the UCHART statement, must also be a SAS variable in the DATA= data set. Each observation in a DATA= data set must contain a value for each response and a value for the group-variable. The data set should contain one observation per group. When you use a DATA= data set with the UCHART statement, the GROUPN= option (which specifies the number of inspection units per group) is required. Other variables that can be read from a DATA= data set include

  • _PHASE_ (if the READPHASES= option is specified)

  • block-variables

  • symbol-variable

  • BY variables

  • ID variables

For an example of a DATA= data set, see Creating ANOM Charts for Rates from Group Counts.

LIMITS= Data Set

You can read decision limits (or parameters from which the decision limits can be calculated) from a LIMITS= data set specified in the PROC ANOM statement. For example, the following statements read decision limit information from the data set Conlims: 

proc anom data=Info limits=Conlims;
   uchart Defects*Treatment / groupn = 30;
run;

The LIMITS= data set can be an OUTLIMITS= data set that was created in a previous run of the ANOM procedure. Such data sets always contain the variables required for a LIMITS= data set. The LIMITS= data set can also be created directly using a DATA step. When you create a LIMITS= data set, you must provide one of the following:

  • the variables _LDLU_, _U_, and _UDLU_, which specify the decision limits

  • the variable _U_, without providing the variables _LDLU_ and _UDLU_, which is used to calculate the decision limits (see Decision Limits)

In addition, note the following:

  • The variables _VAR_ and _GROUP_ are always required. These must be character variables whose lengths are no greater than 32.

  • _LDLU_ and _UDLU_ must be specified together; otherwise their values are computed.

  • _ALPHA_ is optional but is recommended in order to maintain a complete set of decision limit information. The default value is 0.05.

  • _LIMITK_ is optional. The default value is k, the number of groups. A group must have at least one nonmissing value ($n_{i} \geq 1$) and there must be at least one group with $n_{i} \geq 2$. If specified, _LIMITK_ overrides the value of k.

  • _LIMITN_ is optional. The default value is the common group size (n), in the balanced case $n_{i} \equiv n$. If specified, _LIMITN_ overrides the value of n.

  • The variable _TYPE_ is optional, but is recommended to maintain a complete set of decision limit information. The variable _TYPE_ must be a character variable of length 8. Valid values are 'ESTIMATE,' 'STANDARD,' 'STDMEAN,' and 'STDRMS.' The default is 'ESTIMATE.'

  • The variable _INDEX_ is required if you specify the READINDEX= option; this must be a character variable whose length is no greater than 48.

  • BY variables are required if specified with a BY statement.

SUMMARY= Data Set

You can read group summary statistics from a SUMMARY= data set specified in the PROC ANOM statement. This enables you to reuse OUTSUMMARY= data sets that have been created in previous runs of the ANOM procedure or to read output data sets created with SAS summarization procedures.

A SUMMARY= data set used with the UCHART statement must contain the following variables:

  • group-variable

  • response rates for each response

  • number of occurrence units for each response

The names of the variables containing the rates and number of occurrence units must be the response name concatenated with the special suffix characters U and N, respectively. For example, consider the following statements: 

proc anom summary=Summary;
   uchart (Flaws Ndefects)*Treatment;
run;

The data set Summary must include the variables Treatment, FlawsU, FlawsN, NdefectsU, and NdefectsN.

Note that if you specify a response name that contains 32 characters, the names of the summary variables must be formed from the first 16 characters and the last 15 characters of the response name, suffixed with the appropriate character.

Other variables that can be read from a SUMMARY= data set include

  • _PHASE_ (if the READPHASES= option is specified)

  • block-variables

  • symbol-variable

  • BY variables

  • ID variables

TABLE= Data Set

You can read group statistics and decision limits from a TABLE= data set specified in the PROC ANOM statement. This enables you to reuse an OUTTABLE= data set created in a previous run of the ANOM procedure or to create your own TABLE= data set. Because the ANOM procedure simply displays the information read from a TABLE= data set, you can use TABLE= data sets to create specialized ANOM charts.

Table 4.24 lists the variables required in a TABLE= data set used with the UCHART statement.

Table 4.24: Variables Required in a TABLE= Data Set

Variable

Description

Group-variable

Values of the group-variable

_LDLU_

Lower decision limit for rate

_LIMITN_

Nominal number of opportunity units associated with the decision limits

_SUBN_

Number of opportunity units in group

_SUBU_

Response rate for group

_U_

Weighted average of group rates

_UDLU_

Upper decision limit for rate


Other variables that can be read from a TABLE= data set include

  • block-variables

  • symbol-variable

  • BY variables

  • ID variables

  • _PHASE_ (if the READPHASES= option is specified). This variable must be a character variable whose length is no greater than 48.

  • _VAR_. This variable is required if more than one response is specified or if the data set contains information for more than one response. This variable must be a character variable whose length is no greater than 32.

For an example of a TABLE= data set, see Saving Decision Limits.