来自同级XML项的数据帧

我有几个XML项

系列

结构为

<Series>
  <SeriesKey>
  <Value concept="LOCATION" value="NOR"/>
  <Value concept="TRANSACT" value="B1_GA"/>
  <Value concept="MEASURE" value="CXC"/>
  </SeriesKey>
  <Attributes>
  <Value concept="TIME_FORMAT" value="P1Y"/>
  <Value concept="UNIT" value="USD"/>
  <Value concept="POWERCODE" value="6"/>
  </Attributes>
  <Obs>
  <Time>1970</Time>
  <ObsValue value="12729.77490809"/>
  </Obs>
  <Obs>
  <Time>1971</Time>
  <ObsValue value="14505.3225330031"/>
  </Obs>
  <Obs>
  <Time>1972</Time>
  <ObsValue value="17219.5954919744"/>
  </Obs>
  </Series>
<Series>
  <SeriesKey>
   <Value concept="LOCATION" value="USA"/>
   <Value concept="TRANSACT" value="B1_GA"/>
   <Value concept="MEASURE" value="CXC"/>
  </SeriesKey>
  <Attributes>
   <Value concept="TIME_FORMAT" value="P1Y"/>
   <Value concept="UNIT" value="USD"/>
   <Value concept="POWERCODE" value="6"/>
   </Attributes>
    ...
  </Series>

从存储在这里的原始文档

url <- "http://stats.oecd.org/restsdmx/sdmx.ashx/GetData/SNA_TABLE1/NOR+CAN+FRA+DEU+GBR+USA+ITA+JAP.B1_GA+B1G_P119+B1G+B1GVA+B1GVB_E+B1GVC+B1GVF+B1GVG_I+B1GVJ+B1GVK+B1GVL+B1GVM_N+B1GVO_Q+B1GVR_U+D21_D31+D21S1+D31S1+DB1_GA.CXC/all?startTime=1950&endTime=2013"

---

但是我找不到任何简单的方法将每个

Obs

分配给它的

序列键

远不是优雅的，但仍然

df <- data.frame()

for (i in 1:length(xpathSApply(xml, "//message:MessageGroup/def:DataSet/def:Series", namespaces=ns))) {
  location <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:SeriesKey/def:Value[@concept='LOCATION']/@value"), namespaces=ns)
  transact <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:SeriesKey/def:Value[@concept='TRANSACT']/@value"), namespaces=ns)
  measure <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:SeriesKey/def:Value[@concept='MEASURE']/@value"), namespaces=ns)

  time <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:Obs/def:Time"), xmlValue, 
                      namespaces=ns)
  value <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:Obs/def:ObsValue/@value"), 
                       namespaces=ns)

  tmp <- data.frame(location=rep(location, length(time)),
                    transact=rep(transact, length(time)),
                    measure=rep(measure, length(time)),
                    time=time,
                    value=value)

  df <- rbind(df, tmp)
}

---

df不是很好，但是。。。获取数据和名称空间

xml <- xmlParse(url)
ns <- xmlNamespaceDefinitions(xml, simplify=TRUE)
names(ns)[1] = "def"

xml您在示例xml中没有显示名称空间，但从您的代码看，似乎实际存在名称空间。您是否可以更新以更好地显示xml@RichardScriven整个文件是啊,我明白了。我认为，如果对根文档进行操作，即
xmlRoot
length(xpathSApply(xml, "//message:MessageGroup/def:DataSet/def:Series/def:SeriesKey/def:Value[@concept='LOCATION']/@value", namespaces=ns))
# [1] 123

length(xpathSApply(xml, "//message:MessageGroup/def:DataSet/def:Series/def:Obs", namespaces=ns))
# [1] 3959

df <- data.frame()

for (i in 1:length(xpathSApply(xml, "//message:MessageGroup/def:DataSet/def:Series", namespaces=ns))) {
  location <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:SeriesKey/def:Value[@concept='LOCATION']/@value"), namespaces=ns)
  transact <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:SeriesKey/def:Value[@concept='TRANSACT']/@value"), namespaces=ns)
  measure <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:SeriesKey/def:Value[@concept='MEASURE']/@value"), namespaces=ns)

  time <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:Obs/def:Time"), xmlValue, 
                      namespaces=ns)
  value <- xpathSApply(xml, paste0("//message:MessageGroup/def:DataSet/def:Series[",i,"]/def:Obs/def:ObsValue/@value"), 
                       namespaces=ns)

  tmp <- data.frame(location=rep(location, length(time)),
                    transact=rep(transact, length(time)),
                    measure=rep(measure, length(time)),
                    time=time,
                    value=value)

  df <- rbind(df, tmp)
}

xml <- xmlParse(url)
ns <- xmlNamespaceDefinitions(xml, simplify=TRUE)
names(ns)[1] = "def"

series <- getNodeSet(xml, "//def:Series", namespaces=ns)

q <- ".//def:SeriesKey/def:Value[@concept='LOCATION']/@value"
LOCATION <- sapply(series, xpathSApply, q, namespaces=ns)

LOCATION <- sapply(series, function(elt) xpathSApply(elt, q, namespaces=ns))

q <- ".//def:Obs/def:Time"
TIME <- lapply(series, xpathSApply, q, xmlValue, namespaces=ns)

q <- ".//def:Obs/def:ObsValue/@value"
VALUE <- lapply(series, xpathSApply, q, namespaces=ns)

geom <- sapply(TIME, length)
df <- data.frame(LOCATION=rep(unname(LOCATION), geom),
                 TIME=unlist(TIME, use.names=FALSE),
                 VALUE=unlist(VALUE, use.names=FALSE))

series <- getNodeSet(xml, "//def:Series", namespaces=ns)
geom <- sapply(series, xpathSApply, "count(.//def:Obs)", namespaces=ns)

LOCATION <- xpathSApply(xml, "//def:Value[@concept='LOCATION']/@value",
                        namespaces=ns)
TIME <- xpathSApply(xml, "//def:Time/text()", xmlValue, namespaces=ns)