MATCH D_INT HOUSE FROM_LEFT TO_LEFT FROM_RT TO_RT 0.999 .01 ZERO_VALID

The field HOUSE is compared to the left interval (FROM_LEFT, TO_LEFT) and the right interval (FROM_RT, TO_RT). The left or right flag is set depending on the results.

Left/Right character comparisons (LR_CHAR)

This type of comparison is used in conjunction with geocoding applications for comparing place or ZIP Code information. Census Bureau TIGER files and other geographic reference files contain a left ZIP Code and a right ZIP Code, a left city code and a right city code, and so on. The left code applies if there was a match to the left address range interval, and the right code applies if there was a match to the right address range. A single field on user data file must be matched to the two fields on file B on a character-by-character basis. A single field is specified on the A file and two fields are specified on the B file. There are two modes of comparisons. The first mode EITHER requires that the contents of the file A field match either of the file B fields specified (or both) to receive the full agreement weight. Since persons living on a boundary segment often report the neighboring code, an either/or match on the code is preferable to rejecting the record.

The second mode, BASED_PREV, uses the result of a previously defined D_INT (double interval) comparison result to decide which field to compare. If the address range specified in a D_INT comparison matched to the left interval, then the file A field must match to the first file B field specified to receive the agreement weight. If the comparison matched to the right interval, then the file A field must match the second field specified. Thus, if the left interval matched, the left code must agree, and if the right interval matched, the right code must agree. If neither the left or right interval agrees, the missing weight for the field is assigned.

Example:

MATCH LR_CHAR ZIP_CODE LEFT_ZIP RIGHT_ZIP 0.9 .01 EITHER

The ZIP_CODE field on File A may match to either the LEFT_ZIP field on file B or the RIGHT_ZIP field on file B (or it may match to both).

Example:

MATCH D_INT HOUSE FROM_LEFT TO_LEFT FROM_RT TO_RT 0.999 .01 ZERO_VALID

MATCH LR_CHAR ZIP_CODE LEFT_ZIP RIGHT_ZIP 0.9 .01 BASED_PREV

This is different from the previous example because the mode is BASED_PREV instead of EITHER. The D_INT compare on HOUSE will set the L/R flag, depending on whether the left or right interval matched. The LR_CHAR compare uses the result of the match to decide which field to compare. If the L flag is set, the ZIP_CODE field on File A must match the LEFT_ZIP field on file B. If the R flag is set, the ZIP_CODE must match to RIGHT_ZIP field on file B. If neither flag is set, the missing weight is assigned to the comparison. It is important that the type D_INT compare precedes the type LR_CHAR compare with mode BASED_PREV.

Left/Right uncertainty character comparisons (LR_UNCERT)

This type of comparison is used in conjunction with geocoding applications for comparing place or ZIP Code information. Census Bureau TIGER files and other geographic reference files contain a left ZIP Code and a right ZIP Code, a left city code and a right city code, and so on. This operates identically to the type LR_CHAR comparison, except that the type UNCERT uncertainty character algorithm is used. The threshold parameter is required before the mode, which must be EITHER or BASED_PREV.

Example:

MATCH LR_UNCERT CITY_NAME LEFT_CITY RIGHT_CITY 0.9 .01 700.0 EITHER

The CITY_NAME field on file A may match to either the

LEFT_CITY field on file B or the RIGHT_CITY field on file B (or

it may match to both), using the uncertainty character comparison with a minimum threshold value of 700.

Numeric comparisons (NUMERIC)

This is an algebraic numeric comparison. Leading spaces are converted internally to zeros and the numbers are compared.

Example:

MATCH NUMERIC AGE AGE 0.9 0.05

Prefix comparisons for truncated fields (PREFIX) The PREFIX comparison type is useful for performing character matching on fields that may be truncated. For example, a last name of ABECROMBY could be truncated to ABECROM because of lack of space. The PREFIX comparison type will consider these two representations to be an equal match. The string length to be compared is the shorter of the two strings. No characters are compared after the length of the shorter string.

This is different from CHAR, where these two names would not match. The length is computed by ignoring trailing blanks (spaces). Embedded blanks are not ignored.

Prorated comparisons (PRORATED)

This allows numeric fields to disagree by a specified absolute amount as specified by the additional parameter. For example, if the parameter is 15, then if the absolute value of the difference in the field values is greater than 15, the disagreement weight would be assigned to the comparison. If the difference is zero, then the full agreement weight would be assigned. Any difference between 0 and 15 would receive a weight proportionally equal to the difference. Thus, small differences would be slightly less than the full agreement weight, while large differences would be slightly greater than the full disagreement weight. A difference of 8 would

receive a weight exactly between the agreement and disagreement weight.

Example:

MATCH PRORATED DAY DAY 0.90 0.1 5

The field DAY on file A is compared to the field DAY on file B.

The numeric values may differ by as much as 5. Thus, the weights are prorated from agreement to disagreement from differences between 0 and 5. (This is equivalent to saying DAY + or - 5).

Two additional parameters may be specified if it matters whether the difference is positive or negative. The first parameter is the tolerance if the value on file B is greater than the value on file A.

The second parameter is the tolerance if the value on A is greater than the value on B. For example:

MATCH PRORATED Aday Bday 0.9 0.1 5 7

The B value may exceed the A value by 5 days, but the A value may exceed the B value by 7 days.

Time comparisons (TIME)

This compares times in the form of hours and minutes (or only hours). The time must be in 24-hour format. 0 is midnight and 2359 is 11:59 PM. An additional parameter is required to indicate the maximum acceptable time difference. For example, 60 would tolerate a difference of 60 minutes. Again, the weights are proportionally divided between the full agreement weight and the full disagreement weight. Times may cross midnight. The

difference is always the shortest way around the clock. The difference between 2300 and 0100 is 120 minutes.

Example: