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I'm trying to extract the links from the following webpage http://ipt.humboldt.org.co/ that are of type "Specimen". I can get the table from the webpage using the following code:
library(XML)
sitePage<-htmlParse("http://ipt.humboldt.org.co/")
tableNodes<-getNodeSet(sitePage,"//table")
siteTable<-readHTMLTable(tableNodes[[1]])
However the links are missing after I use the readHTML command.
719
You just put an img tag inside the table cell (< td > tag). The src attribute's value can be any valid URL of an image on the Web , local or remote.
To extract values from a table, use curly braces. If you extract values from multiple table variables, then the variables must have data types that allow them to be concatenated together. Create a table from numeric and logical arrays from the patients file.
It ended up being an intricate XPath expression:
library(XML)
sitePage<-htmlParse("http://ipt.humboldt.org.co/")
hyperlinksYouNeed<-getNodeSet(sitePage,"//table[@id='resourcestable']
//td[5][.='Specimen']
/preceding-sibling
::td[3]
/a
/@href")
but let me explain the XPath expression bit-by-bit:
//table[@id='resourcestable'] -> This way we are getting the main table on the page called 'resourcestable'
//td[5][.='Specimen'] -> Now we are filtering only these rows that have Type as Specimen
/preceding-sibling -> Now we start looking backwards
::td[3] -> 3 steps to be precise counting backwards from where we are. Be careful preceding-sibling start counting backwards therefore td[1] is the Type column, td[2] is the Organisation column and td[3] is the Name column we want.
/a -> now get the included a node
/@href -> and finally more precisely the href attribute content
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