r - 从具有不同数量元素的xml创建数据框
问题描述
我对 R 相当陌生,试图从 xml 文档中获取一些数据到数据框中。当每个节点具有相同数量的子节点时它工作正常,但是当它没有时我遇到了问题。
我正在使用的 R 代码如下:
library(XML)
xml.m_data <- xmlParse(file="mdata.xml")
df.m_data <- xmlToDataFrame(xml.m_data,nodes = getNodeSet(xml.m_data,"//Row"),collectNames=T)
nodeset <- getNodeSet(xml.m_data,"//Row")[[1]]
colnames <- c()
i <- NULL
for(i in 1:(length(df.m_data))){
x <- toString.XMLNode(nodeset[i])
x <- strsplit(x,"\"")[[1]][2]
colnames[i] <- x
}
colnames(df.m_data) <- colnames
rm(colnames)
我试图获得的结果看起来像这样(来自第二个 XML):
CompanyID ProdConsID UnitID UnitName Commodity Facility Source Commercialisation StartDate
1 COMPANY001 E000001 E000001-001 Name_001 Power Producer Fossil Gas False 2010-01-31T23:00:00
2 COMPANY002 E000002 E000002-001 Name_002 Power Producer Fossil Gas False 2010-01-31T23:00:00
3 COMPANY003 E000003 E000003-001 Name_003A Power Producer Fossil Gas True 2009-10-25T23:00:00
4 COMPANY003 E000003 E000003-002 Name_003B Power Producer Fossil Gas True 2009-10-25T23:00:00
有两个xml,第一个我可以处理,第二个不能。
对于第二个,我收到以下错误:
Error in `[<-.data.frame`(`*tmp*`, i, names(nodes[[i]]), value = c("COMPANY001", : duplicate subscripts for columns
示例 1:
<Results>
<Result>
<Row>
<Field Name="CompanyID">COMPANY001</Field>
<Field Name="ProdConsID">E000001</Field>
<Field Name="UnitID">E000001-001</Field>
<Field Name="UnitName">Name_001</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">False</Field>
<Field Name="StartDate">2010-01-31T23:00:00</Field>
</Row>
<Row>
<Field Name="CompanyID">COMPANY002</Field>
<Field Name="ProdConsID">E000002</Field>
<Field Name="UnitID">E000002-001</Field>
<Field Name="UnitName">Name_002</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">False</Field>
<Field Name="StartDate">2010-01-31T23:00:00</Field>
</Row>
<Row>
<Field Name="CompanyID">COMPANY003</Field>
<Field Name="ProdConsID">E000003</Field>
<Field Name="UnitID">E000003-001</Field>
<Field Name="UnitName">Name_003A</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">True</Field>
<Field Name="StartDate">2009-10-25T23:00:00</Field>
</Row>
<Row>
<Field Name="CompanyID">COMPANY003</Field>
<Field Name="ProdConsID">E000003</Field>
<Field Name="UnitID">E000003-002</Field>
<Field Name="UnitName">Name_003B</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">True</Field>
<Field Name="StartDate">2009-10-25T23:00:00</Field>
</Row>
</Result>
</Results>
示例 2:
<Results>
<Result>
<Row>
<Field Name="CompanyID">COMPANY001</Field>
<Field Name="ProdConsID">E000001</Field>
<Field Name="UnitID">E000001-001</Field>
<Field Name="UnitName">Name_001</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">False</Field>
<Field Name="StartDate">2010-01-31T23:00:00</Field>
<Field Name="EndDate">2015-12-09T23:00:00</Field>
</Row>
<Row>
<Field Name="CompanyID">COMPANY002</Field>
<Field Name="ProdConsID">E000002</Field>
<Field Name="UnitID">E000002-001</Field>
<Field Name="UnitName">Name_002</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">False</Field>
<Field Name="StartDate">2010-01-31T23:00:00</Field>
<Field Name="EndDate">2015-12-09T23:00:00</Field>
</Row>
<Row>
<Field Name="CompanyID">COMPANY003</Field>
<Field Name="ProdConsID">E000003</Field>
<Field Name="UnitID">E000003-001</Field>
<Field Name="UnitName">Name_003A</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">True</Field>
<Field Name="StartDate">2009-10-25T23:00:00</Field>
</Row>
<Row>
<Field Name="CompanyID">COMPANY003</Field>
<Field Name="ProdConsID">E000003</Field>
<Field Name="UnitID">E000003-002</Field>
<Field Name="UnitName">Name_003B</Field>
<Field Name="Commodity">Power</Field>
<Field Name="Facility">Producer</Field>
<Field Name="Source">Fossil Gas</Field>
<Field Name="Commercialisation">True</Field>
<Field Name="StartDate">2009-10-25T23:00:00</Field>
</Row>
</Result>
</Results>
非常感谢任何有用的见解。
解决方案
由于语法更简单,我更喜欢 xml2 包而不是 XML。这里的解决方案读取所有“行”父节点,然后解析每个父节点以获得一系列 1 行数据帧,然后将所有结果合并为最终答案。dplyr 包中
的函数可以处理丢失的列。
有关详细信息,请参阅代码注释。bind_rows()
library(xml2)
library(dplyr)
#list of files to process
fnames<-"results2.xml"
doc<-read_xml(fnames)
#find parent nodes
parents<-xml_find_all(doc, ".//Row")
dfs<-lapply(parents, function(parent) {
#find all of the nodes/records under each parent node
titles <- xml_children(parent) %>% html_attr("Name")
values <- xml_children(parent) %>% html_text()
#make data frame of the values and column headings
df<-as.data.frame(t(values), stringsAsFactors = FALSE)
names(df)<-titles
df
})
#Make combinded dataframe
answer<-bind_rows(dfs)
answer
CompanyID ProdConsID UnitID UnitName Commodity Facility Source Commercialisation StartDate EndDate
1 COMPANY001 E000001 E000001-001 Name_001 Power Producer Fossil Gas False 2010-01-31T23:00:00 2015-12-09T23:00:00
2 COMPANY002 E000002 E000002-001 Name_002 Power Producer Fossil Gas False 2010-01-31T23:00:00 2015-12-09T23:00:00
3 COMPANY003 E000003 E000003-001 Name_003A Power Producer Fossil Gas True 2009-10-25T23:00:00 <NA>
4 COMPANY003 E000003 E000003-002 Name_003B Power Producer Fossil Gas True 2009-10-25T23:00:00 <NA>
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