R Get Column Names from data.frame

Question

I have the following code:

install.packages("XML")
library(XML)
install.packages("plyr")
library(plyr)

feed <- "http://feeds.reuters.com/Reuters/worldNews?format=xml"
reuters<-xmlToList(feed)
data <- lapply(reuters[[1]][names(reuters[[1]])=="item"], data.frame)

data

All of the data is output.

How can I get all the title's of data?

I have tried this names(data) but it only outputs "item" "item" "item".

jdharrison · Accepted Answer · 2014-06-09T13:04:25.330

You have a list of data.frames. You can row bind them together:

> names(do.call(rbind.data.frame, data))
[1] "title"           "link"            "description"     "category.text"  
[5] "category..attrs" "pubDate"         "guid.text"       "guid..attrs"    
[9] "origLink"

data1 <- do.call(rbind.data.frame, data)
> head(data1$title)
[1] Niger says will repatriate its illegal migrants from Algeria     
[2] Twin bombing near Kurdish party office in north Iraq kills 30    
[3] Suicide bomber kills four soldiers in Pakistan's tribal northwest
[4] Sisi keeps Egyptian premier to fix economy after turmoil         
[5] Kosovo's Thaci has tough job to form new cabinet, keep promises  
[6] Libyan Supreme Court rules PM's election unconstitutional        
25 Levels: Niger says will repatriate its illegal migrants from Algeria ...

If you just want the titles

xData <- xmlParse(feed)
> head(xpathSApply(xData, "//title", xmlValue))
[1] "Reuters: World News"                                                 
[2] "Reuters: World News"                                                 
[3] "South Africa platinum strike talks in crucial final day of mediation"
[4] "Africa's sports bars, TV shacks step up security for World Cup"      
[5] "Niger says will repatriate its illegal migrants from Algeria"        
[6] "Twin bombing near Kurdish party office in north Iraq kills 30"

Thanks. That is simple enough. Is there any alternative to avoid binding the data frames or is this essential? — user1477388, Jun 09 '14 at 13:00
@user1477388 you can just parse the `XML` and use an `xpath` to get the titles if thats all you want — jdharrison, Jun 09 '14 at 13:05
I was just curious about other methods - trying to learn R. I believe your binding approach is probably best. — user1477388, Jun 09 '14 at 13:05
There are many ways to get the data from an `XML`. Mostly depends on the complexity of the `XML`. One of my favourite answers is http://stackoverflow.com/questions/22643580/combine-values-in-huge-xml-files — jdharrison, Jun 09 '14 at 13:07

David Arenburg · Answer 2 · 2014-06-09T13:14:38.353

You could also retreive only the names without binding the data frames

Titles <- character(length(data))
for (i in seq_len(length(data))) Titles[i] <- as.character(data[[i]]$title)
Titles
[1] "Niger says will repatriate its illegal migrants from Algeria"                     "Twin bombing near Kurdish party office in north Iraq kills 30"                   
[3] "Suicide bomber kills four soldiers in Pakistan's tribal northwest"                "Sisi keeps Egyptian premier to fix economy after turmoil"                        
[5] "Kosovo's Thaci has tough job to form new cabinet, keep promises"                  "Libyan Supreme Court rules PM's election unconstitutional"                       
[7] "Thai junta to explain itself to international rights groups"                      "Well-trained and armed, Taliban tried to hijack plane in Pakistan"               
[9] "Russia would react to NATO build-up near borders: minister"                       "Myanmar military 'tortures civilians': human rights group"                       
[11] "Five jailed for killing Russia's Politkovskaya, mastermind unknown" 
...

score 3 · Answer 3 · answered Jun 09 '14 at 13:19

Here's how I usually do this - quick and easy.

unname(sapply(data, '[[', 'title'))

# [1] South Africa platinum strike talks in crucial final day of mediation
# [2] Africa's sports bars, TV shacks step up security for World Cup      
# [3] Niger says will repatriate its illegal migrants from Algeria        
# [4] Twin bombing near Kurdish party office in north Iraq kills 30       
# [5] Suicide bomber kills four soldiers in Pakistan's tribal northwest   
# [6] Sisi keeps Egyptian premier to fix economy after turmoil            
# 25 Levels: South Africa platinum strike talks in crucial final day of mediation ...

You can access any of the other elements similarly, e.g.

unname(sapply(data, '[[', 'link'))

The `unname` is optional - just tidies up the output a bit :) — jbaums, Jun 09 '14 at 13:21

R Get Column Names from data.frame

3 Answers3