The T_UMD_TEST stored procedure calculates the t-Student statistics of a numeric input
column the values of which are split into two classes. The goal is to evaluate the significance of
the difference of the mean values of the classes.
Syntax
IDAX.T_UMD_TEST(in parameter_string varchar(32672))
Parameter descriptions
- parameter_string
- Mandatory one-string parameter that contains pairs of
<parameter>=<value> entries that are separated by a comma.
- Data type: VARCHAR(32672)
- The following list shows the parameter values:
-
- intable
- Mandatory.
- The name of the input table.
- Data type: VARCHAR(256)
- outtable
- Mandatory.
- The name of the output table to which the t-Student statistics are written.
- The output table contains the T_UMD_TEST column and the PERCENTAGE column.
- If the by parameter is specified, an extra BY column is added to indicate
for which group the t-Student statistics are calculated.
- The T_UMD_TEST column contains a string with the t-Student value and the degree of freedom.
- The PERCENTAGE column indicates the probability that the column has the expected mean value:
- If the percentage ranges from 0 to 0.05, the second class has a significantly bigger mean value
than the first class.
- If the percentage ranges between 0.05 and 0.95, the two classes have the same mean value.
- If the percentage ranges between 0.95 and 1, the second class has a significantly smaller mean
value than the first class.
- Data type: VARCHAR(256)
- incolumn
- Mandatory.
- The numeric column of the input table.
- Data type: VARCHAR(128)
- class
- Mandatory.
- The column of the input table that splits the data into two classes.
- The name of the CLASS column is followed by two class values that are preceded by a colon
(:).
- Data type: VARCHAR(ANY)
- by
- Optional.
- The column of the input table that splits the data into groups for which the stored procedure is
to be done.
- Default: none
- Data type: VARCHAR(128)
Returned information
DOUBLE the probability that the column of the input table has similar mean values in both
classes, or the number of groups in the output table for which t-Student statistics are
calculated.
Example
CALL IDAX.T_UMD_TEST('intable=IRIS, incolumn=petallength,class=class:"virginica":"setosa", outtable=UMD_TEST_RESULT');