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Using Fuzzy Lookups for Record Linkage Expand / Collapse
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Posted Friday, April 10, 2009 8:52 AM
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I'm going to quote my own article "If your data columns are anything aside from strings (datetime, int, etc.) the Mapping Type will only allow exact." I dislike this fact, but its true. So do a view of your data with a convert(varchar, datetimefield,101)
B



Post #694893
Posted Saturday, April 11, 2009 6:35 AM
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excellent idea thanks.
was wondering how it compares when the dates are slightly different. i guess as you said as long as we have other variables like firstname, surname and gender should get a good result
Post #695169
Posted Tuesday, April 14, 2009 12:36 AM
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Hi Brian
thanks for your help with this..I have a querie i am trying to work out not sure if you have come across an issue like this.
I am comparing Surname, given name and Date Of birth. seems like if the given name has a middle name included in the reference field and not in the source given name field it doesnt even seem to compare the other fields as it gives a 0 confidence.
is there a particulare setting i should be using?
Post #696328
Posted Tuesday, April 14, 2009 7:44 AM
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No I have not seen that, it could be that it is dragging the match weight down enough that it is below your threshold for a match?
Regardless they will lower your scores. Can you script them out? I know it is error prone such as Mary Anne is Anne the middle ... Then once you script them to their own field find the person that made the database and give them a good tutorial on atomicity of fields!

B



Post #696522
Posted Tuesday, April 14, 2009 8:04 AM


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bnordberg (4/14/2009)
...find the person that made the database and give them a good tutorial on atomicity of fields!

If only it were that easy!! I deal with data all the time that is very messy because folks don't care as long as it prints on paper OK. They don't consider the benefits of putting data into the appropriate fields. I get data from Electronic Medical Record systems and the majority of important data is entered into comment fields simply because it's easier to enter that way and as long as the printed paper has the info for the doc to read, it's OK in their minds. Of course, that wrecks havoc on any attempt to utilize the data for any other purpose!



"...when ye are in the service of your fellow beings ye are only in the service of your God." -- Mosiah 2:17
Post #696556
Posted Tuesday, April 14, 2009 8:31 AM
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We'd probably have to time travel back to the 70's to chat with the db designers of most hospital EMR systems. Plus all these old MUMPS/CACHE "databases" that make data retrieval real fun! I'm attempting to parse dosage's from SIG/Instruction fields from our medication tables - there are >25,000 different textual ways of telling someone how to take a drug!
My only other recommendation would be to ensure your thresholds/weights are low for first name and higher for the other fields.
B



Post #696591
Posted Tuesday, April 14, 2009 5:20 PM
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I think thats where my problem is..as you said if Mary Jane is in one firstname field and the comparing Firstname has Only Mary. it doesnt seem to match it. I think I need to muck around with the weights.
Post #697151
Posted Tuesday, April 14, 2009 5:23 PM
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Hi Brian

what did you mean by >Can you script them out? I know it is error prone such as Mary Anne is Anne the middle ... Then once you script them to their own field find the person that made the database and give them a good tutorial on atomicity of fields!

regards

Fred
Post #697153
Posted Friday, August 13, 2010 4:40 PM
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Hello Brian, et al,

Thank you for time in this article. It was very helpful.

For posterity's sake, I did want to point out what appears to be a small, but important, wrinkle in the settings provided in your example that I think are worth a mentioning.

In your example, the Similarity Threshold at the component level on the Advanced Tab is set to .52. However, the Minimum Similarity at the join level for the MPI_PT_dob field (date of birth) is set to .2.

According to MSDN:

To satisfy the similarity that is specified at the component level, all rows must have a similarity across all matches that is greater than or equal to the similarity threshold that is specified at the component level. That is, you cannot specify a very close match at the component level unless the matches at the row or join level are equally close.

Fuzzy Lookup Transformation

Now what I got from that was if a .3 similarity match is made at the join level, which is higher than the threshold you have set of .2, Fuzzy Lookup will still not return the record because the similarity at the component level is .52. I did a quick test and this is, in fact, the case.

It appears that each similarity at the join level acts like an additional filter on each field at the join level to further refine the lookup's results, after the similarity at the component level has already reduced the matches for the entire row.
Post #969311
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