I'm building an application that returns results based on a movie input from a user. If the user messes up and forgets to space out the title of the movie is there a way I can still take the input and return the correct data? For example "outofsight" will still be interpreted as "out of sight".
There is no regex that can do this in a good and reliable way. You could try a search server like Solr.
Alternatively, you could do auto-complete in the GUI (if you have one) on the input of the user, and this way mitigate some of the common errors users can end up doing.
Example:
User wants to search for "outofsight"
Starts typing "out"
Sees "out of sight" as suggestion
Selects "out of sight" from suggestions
????
PROFIT!!!
There's no regex that can tell you where the word breaks were supposed to be. For example, if the input is "offlight", is it supposed to return "Off Light" or "Of Flight"?
This is impossible without a dictionary and some kind of fuzzy-search algorithm. For the latter see How can I do fuzzy substring matching in Ruby?.
You could take a string and put \s* in between each character.
So outofsight would be converted to:
o\s*u\s*t\s*o\s*f\s*s\s*i\s*g\s*h\s*t
... and match out of sight.
You can't do this with regular expressions, unless you want to store one or more patterns to match for each movie record. That would be silly.
A better approach for catching minor misspellings would be to calculate Levenshtein distances between what the user is typing and your movie titles. However, when your list of movies is large, this will become a rather slow operation, so you're better off using a dedicated search engine like Lucene/Solr that excels at this sort of thing.
Related
Say I have an incoming string that I want scan to see if it contains any of the words I have chosen to be "bad." :)
Is it faster to split the string into an array, as well as keep the bad words in an array, and then iterate through each bad word as well as each incoming word and see if there's a match, kind of like:
badwords.each do |badword|
incoming.each do |word|
trigger = true if badword == word
end
end
OR is it faster to do this:
incoming.each do |word|
trigger = true if badwords.include? word
end
OR is it faster to leave the string as it is and run a .match() with a regex that looks something like:
/\bbadword1\b|\bbadword2\b|\bbadword3\b/
Or is the performance difference almost completely negligible? Been wondering this for a while.
You're giving the regex an advantage by not stopping your loop when it finds a match. Try:
incoming.find{|word| badwords.include? word}
My money is still on the regex though which should be simplified to:
/\b(badword1|badword2|badword3)\b/
or to make it a fair fight:
/\a(badword1|badword2|badword3)\z/
Once it is compiled, the Regex is the fastest in real live (i.e. really long incoming string, many similar bad words, etc.) since it can run on incoming in situ and will handle overlapping parts of your "bad words" really well.
The answer probably depends on the number of bad words to check: if there is only one bad word it probably doesn't make a huge difference, if there are 50 then checking an array would probably get slow. On the other hand, with tens or hundreds of thousands of words the regexp probably won't be too fast either
If you need to handle large numbers of bad words, you might want to consider splitting into individual words and then using a bloomfilter to test whether the word is likely to be bad or not.
This does not excatly answer your question but this will definitely help solve it.
Take some examples what your are tring to acheive and put them to bench marks.
you can find how to do benchmarking in ruby here
Just put the varoius forms between report block and get the benchmarks and decide yourself what suits you the best.
http://ruby.about.com/od/tasks/f/benchmark.htm
http://ruby-doc.org/stdlib-1.9.3/libdoc/benchmark/rdoc/Benchmark.html
For better solutions use the real data to test.
Benchmarks are always better than discussions :)
If you want to scan a string for occurrences of words, use scan to find them.
Use Regexp.union to build a pattern that will find the strings in your black-list. You will want to wrap the result with \b to force matching word-boundaries, and use a case-insensitive search.
To give you an idea of how Regexp.union can help:
words = %w[foo bar]
Regexp.union(words)
=> /foo|bar/
'Daniel Foo killed him a bar'.scan(/\b#{Regexp.union(words)}\b/i)
=> ["foo", "bar"]
You could also build the pattern using Regexp.new or /.../ if you want a bit more control:
Regexp.new('\b(?:' + words.join('|') + ')\b', Regexp::IGNORECASE)
=> /\b(?:foo|bar)\b/i
/\b(?:#{words.join('|')})\b/i
=> /\b(?:foo|bar)\b/i
'Daniel Foo killed him a bar'.scan(/\b(?:#{words.join('|')})\b/i)
=> ["Foo", "bar"]
As a word of advice, black-listing words you find offensive is easily tricked by a user, and often gives results that are wrong because many "offensive" words are only offensive in a certain context. A user can deliberately misspell them or use "l33t" speak and have an almost inexhaustible supply of alternate spellings that will make you constantly update your list. It's a source of enjoyment to some people to fool a system.
I was once given a similar task and wrote a translator to supply alternate spellings for "offensive" words. I started with a list of words and terms I'd gleaned from the Internet and started my code running. After several million alternates were added to the database I pulled the plug and showed management it was a fools-errand because it was trivial to fool it.
I'm very new to programming and am a beginner in Ruby. I've done a lot of searching to try to find the answers I need, but nothing seems to match what I'm looking for.
I need to make a program for work that will:
Get keywords from the user
Match those keywords with the same keywords in a database of sentences, and then
Spit out randomized sentences that:
contain all the keywords 1 time
do NOT contain keywords not listed
do NOT duplicate keywords
Important to know: Sentences all have a mix of several keywords, NOT one per sentence
1 & 2 are OK, I've been able to do those. My problem is with part 3. I've tried long lists of "if include?" parameters, but it never ends up working and I know there must be a better way to do this.
My grasp of Ruby (and programming generally) is basic and I don't really know what it can and can't do, so any tips or hints in what functions would be useful would be very very much appreciated.
If the match is found, why don't you consecutively pop it out of your array/db? It will ensure no duplication, since that record would not be present to be matched later. No?
Consider this snippet:
db=%q(It is hot today), %q(It is going to rain), %q(Where are you, sonny?), %q(sentence contains is and are)
keyw=%w(is am are)
de=[]
keyw.each do |word|
for index in 0...db.length
if db[index].include?(word)
puts "Matched #{word} with #{db[index]}"
de<<index
end
end
until de.empty?
db.delete_at(de.pop)
end
end
db is database example and keyw contains keywords.
Corresponding output:
Matched is with It is hot today
Matched is with It is going to rain
Matched is with sentence contains is and are
Matched are with Where are you, sonny?
No duplication. :)
I'm trying to find an elegant solution on how to convert something like this
ALL CAPS TEXT. "WHY ANYONE WOULD USE IT?" THIS IS RIDICULOUS! HELP.
...to regular-case. I could more or less find all sentence-starting characters with:
(?<=^|(\. \"?)|(! ))[A-Z] #this regex sure should be more complex
but (standard) Ruby neither allows lookbehinds, nor it is possible to apply .capitalize to, say, gsub replacements. I wish I could do this:
"mytext".gsub(/my(regex)/, '\1'.capitalize)
but the current working solution would be to
"mytext".split(/\. /).each {|x| p x.capitalize } #but this solution sucks
First of all, notice that what you are trying to do will only be an approximation.
You cannot correctly tell where the sentence boundaries are. You can approximate it as The beginning of the entire string or right after a period, question mark, or exclamation mark followed by spaces. But then, you will incorrectly capitalize "economy" in "U.S. economy".
You cannot correctly tell which words should be capitalized. For example, "John" will be "john".
You may want to do some natural language processing to give you a close-to-correct result in many cases, but these methods are only probablistically correct. You will never get a perfect result.
Understanding these limitations, you might want to do:
mytext.gsub(/.*?(?:[.?!]\s+|\z)/, &:capitalize)
I am working on implementing an autocompletion script in javascript. However, some of the names are two word names with a space in the middle. What kind of algorithm can you use to deal with it. I am using a trie to store the names.
The only solutions I could come up with were just saying that two word names cannot be used (either run them together or put a dash in the middle). The other idea was to create a list of these kind of names and have a separate loop to check the input. The other and possibly best idea I have is to redesign it slightly and have categories for first and last names and then an extra name category. I was wondering if there was a better solution out there?
Edit: I realized I wasn't very clear on what I was asking. My problem isn't adding two word phrases to the trie, but returning them when someone is typing in a name. In the trie I split the first and last names so you can search by either. So if someone types in the first name and then a space, how would I tell if they are typing in the rest of the first name or if they are now typing in the last name.
Why not have the trie also include the names with spaces?
Once you have a list of candidates, split each of them on the space and show the first token...
Is there a reason you are rolling your own autocomplete script, instead of using a currently existing one, such as YUI autocomplete? (i.e. are you doing it just for fun?, etc.)
If you have a way to parse the two-word names, then just include spaces in your trie. But if you cannot determine what is a two-word name and what is two separate words, and your trie cannot be large enough to hold all two-word sequences, then you have a problem.
One simple way to solve this is to default to allowing two-word pairs, but if you have too much branching after the space, throw away that entire branch. This way, when the first word is predictive for the second, you'll get autocompletion, but when it could be any of a huge number of things, your trie will end at the end of a single word.
If you using multiline editor, i guess the best choice autocomplete items will be a word. So firstname, middlename and lastname must be parsed and add a lookup item.
For (one line) textbox use you can add whitespaces (and firstname + space + middlename + space + lastname pattern) in search criteria.
I need to parse some text from pdfs but the pdf formatting results in extremely unreliable spacing. The result is that I have to ignore the spaces and have a continuous stream of non-space characters.
Any suggestions on how to parse the string and put spaces back into the string by guessing?
I'm using ruby. Or should I say I'musingruby?
Edit: I've pulled the text out using pdf-reader. Some of the pdf files are nicely formatted and some are not. An example of text mixed with positioning:
.7aspe-5.5cts-715.1o0.6f-708.5f-0.4aces-721.4that-716.3are-720.0i-1.8mportant-716.3in-713.9soc-5.5i-1.8alcommunica6.6tion6.3.-711.6Althoug6.3h-708.1m-1.9od6.3els-709.3o6.4f-702.8f5.4ace-707.9proc6.6essing-708.2haveproposed-611.2ways-615.5to-614.7deal-613.2with-613.0these-613.9diff10.4erent-613.7tasks,-611.9it-617.1remainsunclear-448.0how-450.7these-443.2mechanisms-451.7might-446.7be-447.7implemented-447.2in-450.3visualOne-418.9model-418.8of-417.3human-416.4face-421.9processing-417.5proposes-422.7that-419.8informa-tion-584.5is-578.0processed-586.1in-583.1specialised-584.7modules-577.0(Breen-584.4et-582.9al.,-582.32002;Bruce-382.1and-384.0Y92.0oung,-380.21986;-379.2Haxby-379.9et-380.5al.,-
and if I print just string data (I added returns at the end of each line to keep it from
messing up the layout here:
'Distinctrepresentationsforfacialidentityandchangeableaspectsoffacesinthehumantemporal
lobeTimothyJ.Andrews*andMichaelP.EwbankDepartmentofPsychology,WolfsonResearchInstitute,
UniversityofDurham,UKReceived23December2003;revised26March2004;accepted27July2004Availab
leonline14October2004Theneuralsystemunderlyingfaceperceptionmustrepresenttheunchanging
featuresofafacethatspecifyidentity,aswellasthechangeableaspectsofafacethatfacilitates
ocialcommunication.However,thewayinformationaboutfacesisrepresentedinthebrainremainsc
ontroversial.Inthisstudy,weusedfMRadaptation(thereductioninfMRIactivitythatfollowsthe
repeatedpresentationofidenticalimages)toaskhowdifferentface-andobject-selectiveregionsofvisualcortexcontributetospecificaspectsoffaceperception'
The data is spit out by callbacks so if I print each string as it is returned it looks like this:
'The
-571.3
neural
-573.7
system
-577.4
underly
13.9
ing
-577.2
face
-573.0
perc
13.7
eption
-574.9
must
-572.1
repr
20.8
esent
-577.0
the
unchangin
14.4
g
-538.5
featur
16.5
es
-529.5
of
-536.6
a
-531.4
face
'
On examination it looks like the true spaces are large negative numbers < -300 and the false spaces are much smaller positive numbers. Thanks guys. Just getting to the point where i am asking the question clearly helped me answer it!
Hmmmm... I'd have to say that guessing is never a good idea. Looking at the problem root cause and solving that is the answer, anything else is a kludge.
If the spacing is unreliable from the PDF, how is it unreliable? The PDF viewer needs to be able to reliably space the text so the data is there somewhere, you just need to find it.
EDIT following comment:
The idea of parsing the file using a dictionary (your only other option really, apart from randomly inserting spaces and hoping for the best) and inserting spaces at identified word boundaries (a real problem when dealing with punctuation, plurals that don't alter the base word i.e. plural, etc) would, I believe, be a much greater programming challenge than correctly parsing the PDF in the first place. After all, PDF is clearly defined whereas English is somewhat wooly.
Why not look down the route of existing solutions like ps2ascii in linux, call the function from your Ruby and pick up the result.
PDF doesn't only store spaces as space characters, but also uses layout commands for spacing (so it doesn't print a space, but moves the "pen" to the right). Perhaps you should have a look at the PDF reference (the big PDF on the bottom of the site), Chapter 9 "Text" should be what you're looking for.
EDIT: After reading your comment to Lazarus' answer, this doesn't seem to be what you're looking for. I think you should try to get a word list from somewhere and try to split your text using it. A good strategy would be to do that using recursion, because for example:
"meandyou"
The first word could be "me" or "mean", but if you try "mean", "dyou" doesn't make sense, so it will be "me", same for the next word that could be "a" or "an" or "and", only "and" makes sense.
If it were me I'd go back to the source PDFs and try a different method of extracting the text, such as iText (for Java) or maybe some kind of PDF-to-HTML to text conversion software method.