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Meva denies to work if the input data are very large (this limit can be changed by the administrator). In this case you can compress the data using MePrep, the Meva Preprocessor, locally onto your computer before sending them to Meva. The compression reduces your data usually onto 1 - 20% of the original file size. F.i. if Meva is restricted to accept not more than 5MB from the user, you can send virtual 25 - 500MB to Meva anyway. In general, if you have large data to analyze or repeated consultations with same data but different parameters, it is recommended to use MePrep since it will decrease the net traffic load and increase the processing speed of client and server.
Despite the fact of the restricted input size, Meva has output limitations as well to protect web clients from dealing with megs of data. The output limitations relate only to HTML mode, not to text mode result.
Download the executable meprep.exe [7kB; MD5: e2ae4c107bf51ec098178d4d76972dad] onto your computer. There is no special setup procedure needed. Put the executable simply into a directory of your choice, f.i. in the same directory, which you download your PubMed result files into.
If your PubMed files have the file extension .fcgi (Default by PubMed), you can facilitate the handling at a later time, if you double click onto such a file, choose "Other..." in the "Open with" dialogue and select the path to MePrep. All you have to do later on if you will start MePrep for that file is to perform a simple double click on this .fcgi file.
MePrep compresses PubMed files by extracting only these fields the user wishes to analyze (and thereby dropping the others). So you must tell MePrep which input file it shall extract from, which fields shall be extracted and which output file shall these fields be written to. This is done by passing 4 parameters:
You can find the short names of the fields in the Field Help.
Drag and drop the file to be compressed onto the MePrep executable (or simply double click onto the file, if you have customized you File Explorer that way - see above). MePrep will start and ask for its outstanding parameters: Press either the ENTER key to accept the defaults or enter own values.
Three examples follow. You have searched in PubMed for articles related to Multiple Sclerosis of the year 2002 and saved your result as MS_2000.fcgi. This file shall now serve as input file for MePrep and MePrep shall generate a compressed output file serving as input for Meva.
(Hint: You will not be asked for File to read [query.fcgi]: if you double clicked that file or dragged that file onto the executable since MePrep already knows the input file name in this case.)
In the 1st example, all fields excepted Abstracts shall be extracted. This is sensible if you want to perform different analyses with the same PubMed data:
* Meva Preprocessor V1.0. Type meprep -? for help. File to read [query.fcgi]: MS_2000.fcgi Field 1 [Delete only AB's]: File to write [MS_2000.meva]: Deleted only AB's. Compressed 10238kB of MS_2000.fcgi onto 4576kB (44%) in MS_2000.meva. Press a key to continue..
In the 2nd example, only MeSH Terms (MH) and Authors (AU) shall be extracted, the rest is dropped. As you can see, MePrep suggests an output file name with trailing field short names:
* Meva Preprocessor V1.0. Type meprep -? for help. File to read [query.fcgi]: MS_2000.fcgi Field 1 [Delete only AB's]: MH Field 2 [NONE]: AU File to write [MS_2000-MH-AU.meva]: Counted 3908 records. Extracted 41488 'MH's. Extracted 17267 'AU's. Compressed 10238kB of MS_2000.fcgi onto 1586kB (15%) in MS_2000-MH-AU.meva. Press a key to continue..
In our last example, only countries (CY) shall be extracted. The compression ratio of 100:1 is superb, however you can consult Meva now with this file only for countries. If you are interested in analyzing other fields as well, MePrep had to be run again with different field name parameters:
* Meva Preprocessor V1.0. Type meprep -? for help. File to read [query.fcgi]: MS_2000.fcgi Field 1 [Delete only AB's]: CY Field 2 [NONE]: File to write [MS_2000-CY.meva]: Counted 3908 records. Extracted 3853 'CY's. Compressed 10238kB of MS_2000.fcgi onto 127kB (1%) in MS_2000-CY.meva. Press a key to continue..
Alternatively you can pass MePrep its parameters directly on the command line (DOS prompt, command shell or whatever you call it). If not supplied, MePrep will ask for the missing parameters. Entering meprep -? on the command line will print a little help screen:
Meva Preprocessor V1.0.
Usage: meprep [-?] [infile pubmed_field1 pubmed_field2 outfile]
Example to extract MeSH Terms and Authors from query.fcgi into mh-au.txt:
meprep query.fcgi MH AU mh-au.txt
For missing parameters MePrep will ask interactively.
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