Ovid search tips

Truncation

Using the $ character and numbers in truncation
 

Any search statement may be truncated by entering 
the truncation character $ at the end of the statement. 
Truncation is used to ensure retrieval of all possible 
variations of a term or, in the case of a phrase-indexed 
field, of the entire phrase.

Truncation can be used with any digit to indicate the 
maximum number of characters that may follow the 
search term or phrase. 

The colon (:) can also be used for right-sided truncation. 

Word-truncation is used most frequently to retrieve 
word variations.

For example, to retrieve "hypnotize," "hypnotized,"
"hypnotizing", and any similar variation such as 
"hypnotics" or "hypnosis",
you could use truncation: 

e.g., hypno$.ti. or hypno$6.ti. 

Truncation is also used with phrase-indexed fields 
to retrieve all forms of a phrase: 

e.g., journal of pharmac$.jn. retrieves
"Journal of Pharmacy and Pharmacology;" 
"Journal of Pharmacological Methods", etc. 

e.g., burroughs j$.au. retrieves
"burroughs j" or "burroughs john" or "burroughs j m". 

Truncation should be used with caution. If you truncate 
too near the beginning of a word or phrase, particularly 
if you fail to limit truncation with a number, your search 
may result in a high number of irrelevant documents. 

For example, rat$ would
retrieve "rat", "rats", "ratio", "rational", "rationale", "rate", etc. 

Use of the # and ? characters in truncation
 

A wild card in the form of the pound sign (#) can be used 
to substitute for one character, and is useful for some plural forms.

For example, wom#n will retrieve "woman" or "women." 

Another wild card is the question mark (?), which is used 
as a replacement for 1 character or no characters. This wild 
card character is useful for British/American word variants, 
since it specifies that you want retrieval whether an extra 
character is there or not.
For example, to locate occurrences of "color or colour" 
you could enter: colo?r, and both "color" and "colour"
will be retrieved. 

Either the ? wild card or the truncation symbol may be used 
for common plurals. 
For example, hospital$1 or hospital? will
both retrieve "hospital" or "hospitals." 

Note that it is not possible to apply the ? character in a word 
if there is only one letter in front of the truncation. For example,
f?etal is not acceptable. 



Boolean and Positional Operators

There are four permissible boolean and positional operators: 
AND, OR, NOT and ADJ. 

By combining two sets using "OR" logic, a third set 
will be created which contains all the documents from 
both sets (with duplicates eliminated). 

By combining two sets using "AND" logic, a third
set will be created which contains documents the two
sets have in common. 

The use of "NOT" logic may be used to exclude the
documents of one set from a second set. 

There is no predefined order of precedence for the 
boolean and positional operators. You may, however, 
specify precedence by using parentheses. Note also that 
there is no default boolean operator.

Thus, the statement 
(iv or intravenous or intra adj venous).ti. 
evokes an error because the ADJ operator is read last. 

The Adjacency operator (ADJ) may be used in searching 
the title or abstract fields. "Proximity" syntax may be used 
for finding two adjacent words in the title of an article. 

For example: 

     temporal (ti) adj lobe (ti) 


will retrieve documents where the word "temporal" 
appears next to the word "lobe" in the title. 

When ADJ is used alone, the terms entered will be found 
in the specified order, excluding intervening stopwords. 
The Adjacency operator may be used with a number (up to 99), 
to retrieve adjacent terms in any order. 

For example:
"ADJ10" 

will find terms that are within ten words of each other. 

Note that because the ADJ operator may be used only in
searching titles and abstracts, each term in an adjacency
statement must be field qualified, or the entire phrase must 
be enclosed in parentheses. 

The following examples illustrate the use of these operators, 
including the use of nesting: 


     (aids or grid).ti.
     1 or aids.ti.
     temporal.ti. adj lobe.ti.
     (heart adj10 attacks).ab.
     1 and 2 or 3
     (1 and 2) or 3
     1 and (2 or 3)
     (1 and (2 or 3)) or 4
     Brook-im.au. and (diazepam.ti,rn. or temazepam.ti,rn.)




The Frequency Operator

The Frequency Operator allows you to specify a threshold 
of occurrence for a term. This operator is particularly useful 
when lengthy documents are being searched for a somewhat 
common concept. Using the Frequency Operator ensures that 
a word or phrase will only be retrieved if it occurs at least an 
indicated number of times. For example, the statement: 

     text analysis.ab./freq=3


will only retrieve documents in which the phrase "text analysis" 
appears in the abstract at least three times. 

Postqualified statements may also contain the frequency operator, 
for example: 


     You enter:  Ovid displays the search as:
     ----------      ----------------------------
     1. heart.ab.    heart.ab.
     2. 1 /freq=2    heart.ab. /freq=2


HINT: Contact the librarians to determine other appropriate techniques.


| Science Libraries Home Page | Main Library Front Door |

created by Andy Shimp, revised by:  david.e.stern@yale.edu

last modification date:  November 8 1996 



http://www.library.yale.edu/scilib/help/ovidtips.html">search tips.