Modifying XML nodes using R

Assuming the variable xml contains your example:

# xml <- '<h2>...'
library(XML)
doc <- xmlParse(xml, asText = TRUE)
invisible(removeNodes(doc['//step/p']))
saveXML(doc, file = tf <- tempfile(fileext = ".xml"))
# <?xml version="1.0"?>
# <h2>
#   <h4>
#     <stepgrp type="ordered-legal">
#       <figgrp-inlist>
#         <step>
#           <graphic version="1" object-id="4188"/>
#         </step>
#         <stepgrp2 type="unordered-bullet">
#           <step/>
#           <step>
# Two piece case  use J42628 Disc.
# </step>
#         </stepgrp2>
#       </figgrp-inlist>
#       <figgrp-inlist>
#         <step>
#           <graphic version="1" object-id="59269"/>
#         </step>
#         <step>
# Remove the low/reverse clutch retainer ring.
# </step>
#         <step>
# Remove the low/reverse the clutch spring assembly.
# </step>
#       </figgrp-inlist>
#       <figgrp-inlist>
#         <step>
#           <graphic version="1" object-id="4190"/>
#         </step>
#       </figgrp-inlist>
#     </stepgrp>
#   </h4>
# </h2>

The output is stored in the filename, which is in tf (temporary file).

Add

With regards to your comment, try:

doc <- xmlParse(xml, asText = TRUE)
nodes <- doc['//step']
idx <- which(sapply(nodes, function(x) 'p' %in% names(xmlChildren(x))))
vals <- sapply(nodes[idx], xmlValue)
removeNodes(doc['//step/p'])
for (x in seq_len(length(vals)))
  newXMLTextNode(text = vals[x], doc['//step'][[idx[x]]])

There may be a more elegant version, though.

please find the answer my friend came up with and it sure works!

t1 <- readLines('xml')

t2 <-paste(t1,collapse = "\n")
t3 <- regmatches(t2, regexpr('<step>.+</step>', t2))
t4 <- as.character(unlist(strsplit(as.character(t3),"\n")))

torf <- t1 %in% t4

t5 <- character(length(t1))

for(i in 1 :length(t1)){
  if(torf[i]){
    t5[i] <- t1[i]
  } else {
    t5[i] <- t5[i]
  }
}


removep <- function(x){
  x1 <- gsub("<p>","",x)
  x2 <- gsub("</p>","",x1)
  return (x2)
}

t5 <- removep(t5)

for(i in 1:length(t5)){
  if(t5[i]!=""){
    t5[i] <- t5[i]
  } else {
    t5[i] <- t1[i]
  }
}