XPath, select two consecutive elements and transform them into one data frame

问题

I am really new to Path and R in general and am trying to convert an XML file using XPath into a data frame in R. With some help I managed to transform most of the information in the XML already . However, now I am trying to take two consecutive elements and merge them into one data frame. Somehow I can't seem to get it right.

This is an excerpt of the xml data:

</customer-bootstrap-data>
  <customer-bootstrap-data id="970911" customerName="HighIncome-1_4" powerType="ELECTRIC_VEHICLE">
<netUsage>0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.1124173640233721,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.37606842556525066,-0.0,-0.0,-0.038684343289247636,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.8490012729862713,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0</netUsage>
  </customer-bootstrap-data>
  <customer-bootstrap-data id="970912" customerName="HighIncome-2_17" powerType="ELECTRIC_VEHICLE">
<netUsage>0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.21395291779884928,-0.0,-0.0,-1.3581716633726693,-0.0,-0.0,-2.8140822306420716,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.0221045637055397,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.3,-3.3,-3.223543705462774,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.153329511039221,-0.0,-0.0,-0.0,-0.0,-0.0,-0.820425411761537,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.7054631085029754,-0.0,-0.7130641168720118,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-2.5003661751788435,-0.0,-0.0,-3.3,-3.3,-0.6606989045692728,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.20818145620010853,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0493154269844851,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.3,-0.0,-1.041919182358086,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.3,-0.5334016276259916,-0.0,-0.0,-0.0</netUsage>
  </customer-bootstrap-data>

I am able to generate a table with the first element using the following code:

customerBoot <- xpathSApply(doc=xml, path=("//customer-bootstrap-data"), xmlAttrs)
customerBoot <- data.frame(t(customerBoot))

containing id, customerName and powerType. But I want the net usage to be also included for each customer id.

The following code selects all the information I want it just doesn't allow me to transform it into a data frame.

customerBoot <- getNodeSet(xml,"//customer-bootstrap-data")

Any ideas going either way? I am looking for a fast solution.

Thank you!

回答1:

Let me know if this has speed issues (iterating over a huge XML doc in this manner can sometimes be slow):

library(XML)
library(purrr)

fil <- '<dat><customer-bootstrap-data id="970911" customerName="HighIncome-1_4" powerType="ELECTRIC_VEHICLE">
<netUsage>0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.1124173640233721,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.37606842556525066,-0.0,-0.0,-0.038684343289247636,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.8490012729862713,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0</netUsage>
  </customer-bootstrap-data>
  <customer-bootstrap-data id="970912" customerName="HighIncome-2_17" powerType="ELECTRIC_VEHICLE">
<netUsage>0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.21395291779884928,-0.0,-0.0,-1.3581716633726693,-0.0,-0.0,-2.8140822306420716,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.0221045637055397,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.3,-3.3,-3.223543705462774,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.153329511039221,-0.0,-0.0,-0.0,-0.0,-0.0,-0.820425411761537,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.7054631085029754,-0.0,-0.7130641168720118,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-2.5003661751788435,-0.0,-0.0,-3.3,-3.3,-0.6606989045692728,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.20818145620010853,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0493154269844851,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.3,-0.0,-1.041919182358086,-0.0,-0.0,-0.0,-0.0,-0.0,-0.0,-3.3,-0.5334016276259916,-0.0,-0.0,-0.0</netUsage>
  </customer-bootstrap-data></dat>'

doc <- xmlParse(fil)

customerBoot <- xpathSApply(doc=doc, path="//customer-bootstrap-data", xmlAttrs)
customerBoot <- data.frame(t(customerBoot), stringsAsFactors=FALSE)

# go by row using the id, grab the desired data node, convert it to a wide data.frame

customerBoot <- purrr::by_row(customerBoot, function(x) {

  path <- sprintf("//customer-bootstrap-data[@id='%s']/netUsage", x$id)
  vals <- strsplit(xpathSApply(doc=doc, path=path, xmlValue), ",")[[1]]
  as.numeric(vals)

}, .to="X", .collate="cols")

# limiting the "str()" equivalent "glimpse()" to 15 columns since there are >300 of them:

dplyr::glimpse(customerBoot[, 1:15])

## Observations: 2
## Variables: 15
## $ id           (chr) "970911", "970912"
## $ customerName (chr) "HighIncome-1_4", "HighIncome-2_17"
## $ powerType    (chr) "ELECTRIC_VEHICLE", "ELECTRIC_VEHICLE"
## $ X1           (dbl) 0, 0
## $ X2           (dbl) 0, 0
## $ X3           (dbl) 0, 0
## $ X4           (dbl) 0, 0
## $ X5           (dbl) 0, 0
## $ X6           (dbl) 0, 0
## $ X7           (dbl) 0, 0
## $ X8           (dbl) 0.0000000, -0.2139529
## $ X9           (dbl) 0, 0
## $ X10          (dbl) 0, 0
## $ X11          (dbl) 0.000000, -1.358172
## $ X12          (dbl) 0, 0

Alternate way with xml2:

library(purrr)
library(xml2)

doc <- read_xml(fil)

xml_find_all(doc, "//customer-bootstrap-data") %>% 
  xml_attrs() %>% 
  map_df(function(x) {
    path <- sprintf("//customer-bootstrap-data[@id='%s']/netUsage", x["id"])
    vals <- strsplit(xml_text(xml_find_one(doc, path)), ",")[[1]]
    vals <- setNames(as.numeric(vals), sprintf("X%d", 1:length(vals)))
    rbind.data.frame((c(as.list(x), as.list(vals))), stringsAsFactors=FALSE)
  })

UPDATE:

Here's one way to do it when netUsage is not of uniform length:

data.table::rbindlist(apply(customerBoot, 1, function(x) {

  path <- sprintf("//customer-bootstrap-data[@id='%s']/netUsage", x["id"])
  vals <- strsplit(xpathSApply(doc=doc, path=path, xmlValue), ",")[[1]]
  c(as.list(x), as.list(setNames(as.numeric(vals), sprintf("X%d", 1:length(vals)))))

}), fill=TRUE)

来源：https://stackoverflow.com/questions/37565910/xpath-select-two-consecutive-elements-and-transform-them-into-one-data-frame

标签

xml

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elements