MATCH

MATCH (LET)

Let Subcommand

Match a column of values to another column of numbers and return the index of the matching value.

This command works on two columns of numbers. The first column contains a set of numbers. Each value in the second column is matched against the first column. The closest value, as determined by the smallest absolute value in the difference between the numbers, is considered the match. This command returns the index, not the actual value, of the first array where the match occurs. The returned column of numbers will then be an array of index numbers.

This is a utility operation. That is, the index numbers are generally not of interest themselves but are used in subsequent computations.

An alternative syntax supplies a third variable. Instead of returning an index, the MATCH command uses the index to extract the value corresponding to the index of this third variable. Generally, this is the ultimate goal (i.e., we would use the index to extract values of another variable).

LET <y> = MATCH <x> <val>             <SUBSET/EXCEPT/FOR qualification>
where <x> is the variable containing a set of numbers;
            <val> is a number, parameter, or variable that will be matched against the values in <x>;
            <y> is a variable (of length equal to <val>) that contains the index (of <x>) where the match occurs;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

This syntax returns the index value.

LET <y> = MATCH <x> <val> <z>                       <SUBSET/EXCEPT/FOR qualification>
where <x> is the variable containing a set of numbers;
            <val> is a number, parameter, or variable that will be matched against the values in <x>;
            <z> is a variable (of length equal to <x>) that contains the values to be extracted and placed in <y>;
            <y> is a variable (of length equal to <val>) that contains the values of <z> corresponding to the matched indices (of <x>);
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

This syntax returns values of corresponding to the matched indices.

LET Y = MATCH X VALUE
LET Y = MATCH X VALUE SUBSET X > 0 1
LET Y = MATCH X VALUE Z
LET Y = MATCH X VALUE Z SUBSET X > 0

None

None

SEQUENCE	= Generate a patterned sequence of values.
SORT	= Sort a column of numbers.
RANK	= Rank a column of numbers.
CODE	= Code a column of numbers.

Data Transformation

2001/10

LET Y = NORMAL RANDOM NUMBERS FOR I = 1 1 100
LET VAL = SEQUENCE -3 1 3
LET Y2 = MATCH Y VAL
SET WRITE DECIMALS 3
PRINT VAL Y2

LET Y = NORMAL RANDOM NUMBERS FOR I = 1 1 100
LET VAL = SEQUENCE -3 1 3
LET Z = SEQUENCE -10 1 -1
LET Y2 = MATCH Y VAL Z
SET WRITE DECIMALS 3
PRINT Y Z
PRINT VAL Z2