Usually I would expect a `String.contains()` method, but there doesn&#39;t seem to be one. 

What is a reasonable way to check for this?


How to check whether a string contains a substring in JavaScript?

I want to use curl to view the source of a page and if that source contains a word that matches the string then it will execute a print. How would I do a `if $string contains`?

In VB it would be like.

    dim string1 as string = &quot;1&quot;
    If string1.contains(&quot;1&quot;) Then
    Code here...
    End If

Something similar to that but in Perl.

Perl - If string contains text?

Is there a way to retrieve the (starting) character positions inside a string of the results of a regex match() in Javascript?

Return positions of a regex match() in Javascript?

Consider the following snippet:

    &quot;12-18&quot; -Contains &quot;-&quot;

You’d think this evaluates to `true`, but it doesn&#39;t. This will evaluate to `false` instead. I’m not sure why this happens, but it does.

To avoid this, you can use this instead:

    &quot;12-18&quot;.Contains(&quot;-&quot;)

Now the expression will evaluate to true.

Why does the first code snippet behave like that? Is there something special about `-` that doesn&#39;t play nicely with `-Contains`? [The documentation][1] doesn&#39;t mention anything about it.

  [1]: http://technet.microsoft.com/en-us/library/hh847759.aspx


PowerShell and the -contains operator

I am doing clinical message normalization (spell check) in which I check each  given word against 900,000 word medical dictionary. I am more concern about the time complexity/performance.

I want to do fuzzy string comparison, but I&#39;m not sure which library to use.

Option 1:

    import Levenshtein
    Levenshtein.ratio(&#39;hello world&#39;, &#39;hello&#39;)
    
    Result: 0.625

Option 2:

    import difflib
    difflib.SequenceMatcher(None, &#39;hello world&#39;, &#39;hello&#39;).ratio()
    
    Result: 0.625

In this example both give the same answer. Do you think both perform alike in this case?


High performance fuzzy string comparison in Python, use Levenshtein or difflib

I&#39;m looking for a string similarity algorithm that yields better results on variable length strings than the ones that are usually suggested (levenshtein distance, soundex, etc).

For example,

Given string A: &quot;Robert&quot;,

Then string B: &quot;Amy Robertson&quot;

would be a better match than

String C: &quot;Richard&quot;

Also, preferably, this algorithm should be language agnostic (also works in languages other than English).

A better similarity ranking algorithm for variable length strings

I&#39;m looking for a fuzzy search JavaScript library to filter an array. I&#39;ve tried using [fuzzyset.js](http://glench.github.io/fuzzyset.js/) and [fuse.js](https://fusejs.io/), but the results are terrible (there are demos you can try on the linked pages).

After doing some reading on Levenshtein distance, it strikes me as a poor approximation of what users are looking for when they type. For those who don&#39;t know, the system calculates how many **insertions**, **deletions**, and **substitutions** are needed to make two strings match.

One obvious flaw, which is fixed in the Levenshtein-Demerau model, is that both *blub* and *boob* are considered equally similar to *bulb* (each requiring two substitutions). It is clear, however, that *bulb* is more similar to *blub* than *boob* is, and the model I just mentioned recognizes that by allowing for **transpositions**.

I want to use this in the context of text completion, so if I have an array `[&#39;international&#39;, &#39;splint&#39;, &#39;tinder&#39;]`, and my query is *int*, I think *international* ought to rank more highly than *splint*, even though the former has a score (higher=worse) of 10 versus the latter&#39;s 3.

So what I&#39;m looking for (and will create if it doesn&#39;t exist), is a library that does the following:

- Weights the different text manipulations
- Weights each manipulation differently depending on where they appear in a word (early manipulations being more costly than late manipulations)
- Returns a list of results sorted by relevance

Has anyone come across anything like this? I realize that StackOverflow isn&#39;t the place to be asking for software recommendations, but implicit (not anymore!) in the above is: am I thinking about this the right way?

-------------
Edit
----
I found a [good paper (pdf)](https://web.archive.org/web/20160804043501/https://www.cs.cmu.edu/~pradeepr/papers/ijcai03.pdf) on the subject. Some notes and excerpts: 

&gt;Affine edit-distance functions assign a relatively lower cost to a sequence of insertions or deletions

&gt;the Monger-Elkan distance function (Monge &amp; Elkan 1996), which is an affine variant of the Smith-Waterman distance function (Durban et al. 1998) with particular cost parameters

For the [Smith-Waterman distance (wikipedia)](http://en.wikipedia.org/wiki/Smith%E2%80%93Waterman_algorithm), &quot;Instead of looking at the total sequence, the Smith–Waterman algorithm compares segments of all possible lengths and optimizes the similarity measure.&quot; It&#39;s the n-gram approach.

&gt; A broadly similar metric, which is not based on an edit-distance model, is the
Jaro metric (Jaro 1995; 1989; Winkler
1999). In the record-linkage literature, good results have been obtained using variants of this method, which is based on the number and order of the common characters between two strings.

&gt;A variant of this due to Winkler (1999) also uses the length P of the longest common prefix

&gt;(seem to be intended primarily for short strings)

For text completion purposes, the Monger-Elkan and Jaro-Winkler approaches seem to make the most sense. Winkler&#39;s addition to the Jaro metric effectively weights the beginnings of words more heavily. And the affine aspect of Monger-Elkan means that the necessity to complete a word (which is simply a sequence of additions) won&#39;t disfavor it too heavily. 

Conclusion:
&gt;the TFIDF
ranking performed best among several token-based distance
metrics, and a tuned affine-gap edit-distance metric proposed by Monge and Elkan performed best among several
string edit-distance metrics. A surprisingly good distance
metric is a fast heuristic scheme, proposed by Jaro and later extended by Winkler.
This works almost as well as the Monge-Elkan scheme, but
is an order of magnitude faster.
One simple way of combining the TFIDF method and the
Jaro-Winkler is to replace the exact token matches used in
TFIDF with approximate token matches based on the Jaro-
Winkler scheme. This combination performs slightly better than either Jaro-Winkler or TFIDF on average, and occasionally performs much better. It is also close in performance to a learned combination of several of the best metrics
considered in this paper.

Javascript fuzzy search that makes sense

Consider:

    $a = &#39;How are you?&#39;;

    if ($a contains &#39;are&#39;)
        echo &#39;true&#39;;

Suppose I have the code above, what is the correct way to write the statement `if ($a contains &#39;are&#39;)`?


How do I check if a string contains a specific word?

Is it possible to search **every column of every table** for a particular value in PostgreSQL?

A similar question is available [here][1] for Oracle. 

  [1]: https://stackoverflow.com/questions/208493/search-all-fields-in-all-tables-for-a-specific-value-oracle

How to search a specific value in all tables (PostgreSQL)?

How can I check whether a given string contains a certain substring, using Perl?

More specifically, I want to see whether `s1.domain.com` is present in the given string variable.

Check whether a string contains a substring

Given a value I want to validate it to check if it is a valid year. My criteria is simple where the value should be an integer with `4` characters. I know this is not the best solution as it will not allow years before `1000` and will allow years such as `5000`. This criteria is adequate for my current scenario.

What I came up with is

`\d{4}$`

While this works it also allows negative values.

How do I ensure that only positive integers are allowed?

Regular Expression Match to test for a valid year

I have a `data.frame` with character data in one of the columns.
I would like to filter multiple options in the `data.frame` from the same column. Is there an easy way to do this that I&#39;m missing?

**Example:**
`data.frame` name = `dat`

    days      name
    88        Lynn
    11          Tom
    2           Chris
    5           Lisa
    22        Kyla
    1          Tom
    222      Lynn
    2         Lynn


I&#39;d like to filter out `Tom` and `Lynn` for example.   
When I do:

    target &lt;- c(&quot;Tom&quot;, &quot;Lynn&quot;)
    filt &lt;- filter(dat, name == target)

I get  this error:

    longer object length is not a multiple of shorter object length

Filter multiple values on a string column in dplyr

How do I check if a string matches this pattern?

Uppercase letter, number(s), uppercase letter, number(s)...


Example, These would match:

    A1B2
    B10L1
    C1N200J1

These wouldn&#39;t (&#39;^&#39; points to problem)

    a1B2
    ^
    A10B
       ^
    AB400
    ^

Check if string matches pattern

I have several ip addresses like:

1. `115.42.150.37`
2. `115.42.150.38`
3. `115.42.150.50`

What type of regular expression should I write if I want to search for the all the 3 ip addresses? Eg, if I do `115.42.150.*` (I will be able to search for all 3 ip addresses)

What I can do now is something like: `/[0-9]{1-3}\.[0-9]{1-3}\.[0-9]{1-3}\.[0-9]{1-3}/` but it can&#39;t seems to work well. 

Thanks. 

javascript regular expression to check for IP addresses

I want Regular Expression to accept only **Arabic characters**, **Spaces** and **Numbers**.

Numbers are not required to be in Arabic.

I found the following expression:

    ^[\u0621-\u064A]+$

which accepts only only Arabic characters while I need Arabic characters, Spaces and Numbers.

Regular Expression Arabic characters and numbers only

I need to make a conditional that is true if a particular matching text is found at least once in a string of text, e.g.:

    str = &quot;This is some text containing the word tiger.&quot;
    if string.match(str, &quot;tiger&quot;) then
        print (&quot;The word tiger was found.&quot;)
    else
        print (&quot;The word tiger was not found.&quot;)

How can I check if the text is found somewhere in the string?

How to check if matching text is found in a string in Lua?

I am trying to create a regex to have a string only contain `0-9` as the characters and it must be at least 1 char in length and no more than `45`. so example would be `00303039` would be a match, and `039330a29` would not.

So far this is what I have but I am not sure that it is correct

    [0-9]{1,45} 

I have also tried

    ^[0-9]{45}*$

but that does not seem to work either. I am not very familiar with regex so any help would be great. Thanks!


Regex allow a string to only contain numbers 0 - 9 and limit length to 45

I have a data.table with a character column, and want to select only those rows that contain a substring in it.  Equivalent to SQL `WHERE x LIKE &#39;%substring%&#39;`

E.g.

    &gt; Months = data.table(Name = month.name, Number = 1:12)
    &gt; Months[&quot;mb&quot; %in% Name]
    Empty data.table (0 rows) of 2 cols: Name,Number

How would I select only the rows where Name contains &quot;mb&quot;?

All String Matching Solutions on Gang of Coders

Total of 18 String Matching Solutions