Created
February 12, 2013 18:54
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R function to parse out list of specific field/sub-field from MARC/XML
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| library(XML) | |
| getMARCField = function(marc_doc, tag, code) { | |
| xpath = paste("/m:collection/m:record/m:datafield[@tag='", tag, "']/m:subfield[@code='", code, "']", sep="") | |
| return(xpathApply(marc_doc, xpath, namespaces=c("m"), xmlValue)) | |
| } | |
| vs = xmlRoot(xmlParse('vail-first-3500.xml')) | |
| field100a = getMARCField(vs, '100', 'a') |
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After fighting with R's XPath support for a bit, I figured out how to assign the default namespace, which it doesn't do automagically...
Also, using xmlParse, as it turns out, is key to using XPath, since it keeps nodes represented in C-level objects, which allows XPath to work. xmlTreeParse (unless useInternalNodes = FALSE is specified) does not allow this, and is also much slower.