3.5.8.14 Lookup

Lookup-func

Description

This function searches for

• a string pattern str within a vector vs and, if found, returns a value from vector vref with the same index. Vector vref may be contain numeric or string values. If no vref is provided, funtion will return the index of str found in vs. By default, the function searches vs for the full string (option = 2). If no match is found and vref is numeric, the function returns a missing value ("--"); when vref contains strings, an empty string is returned.
• a numeric value dd within a vector vd and, returns a value from vector vref with the same index. If no vref is provided, funtion will return the index of dd in vd. By default, the function seaches vd for the closest value (option = 2). If option = 0, it searchs for the closest value smaller than dd. If option = 1, it searchs for the closest value larger than dd.

The function will return the closest match, using option =0 or =1, but Lookup() does not support wildcard characters.

Syntax

If vref contains numeric values,

 double Lookup(string str$, vector<string> vs[, vector vref, int option, int Case])

If vref contains string values,

 string Lookup(string str$, vector<string> vs[, vector<string> vref, int option, int Case])$

If search a numeric vector vd,

 double Lookup(double dd, vector vd[, vector vref, int option, int Case])

Parameters

str

is the string pattern to find in vector vs.

vs

is the vector in which string pattern str is looked up.

dd

is the double value to find in vector vd.

vd

is the vector in which value dd is looked up.

vref

[optional] the reference vector whose nth value will be returned. n is the index of string str/dd within vector vs/vd. If no vref is provided, funtion will return n.

option

[optional] integer that specifies how the string is matched:

• option = 2 (default), searches for a string that fully matches (see Case).
• option = 0, vector vs is sorted in increasing order. If str is not found, the function will get the index of the nearest value smaller than str.
• option = 1, vector vs is sorted in decreasing order. If str is not found, the function will get the index of the nearest value larger than str.

Case

[optional] integer that specifies whether the search is case sensitive.

• case = 0 (default), the search is not case-sensitive.
• case = 1, the search is case-sensitive.

Return

If str is found in vs, returns a value in vector vref of the same row index.

If option = 2, and str is not found, returns an empty string or missing value.

If option = 0 and str is not found, returns the value corresponding to the nearest smaller value of str. If no smaller value of str exists, returns missing value (numeric) or empty string (string).

If option = 1 and str is not found, returns the value corresponding to the nearest larger value of str. If no larger value of str exists, returns missing value (numeric) or empty string (string).

String Lookup Example

Search elements in Periodic Table Book1 and give the corresponding atomic weight:

Or with Book1 above active, use LabTalk Script to search symbol and output corresponding Name:

range symbol=col(D);
range name=1!col(C);
string str1$ = Lookup("Li", symbol, name)$;
str1$=; // will output Lithium

Numeric Lookup Example

Book1 searches each numeric C value in column B and returns the row index of the finding since the 3rd argument is not specified. 4th argument controls how to find the nearest value: default =nearest value, 0 = nearest value smaller than the specified value, 1 = nearest value larger than the specified value.

Book2 searches each numeric C value in column B and returns the matching A value.

Note: There is index() function to find row index of specified value in data but the data must be strictly monotonic. Skipping 3rd argument to find row index is only supported since Origin 2026.

Labtalk script to search a number in column B and return the row index:

range vd = col(B);
Lookup(0.2, col(B))=;        // nearest (default)
Lookup(0.2, col(B), , 0)=;   // nearest smaller
Lookup(0.2, col(B), , 1)=;   // nearest larger

Labtalk script to search a number in column B and return the corresponding A:

Lookup(0.2, col(B), col(A))=;    // A at matched row

See Also

index (function) list (function) table (function)