R中的readHTMLTable在for循环内引发警告

Question

Hi I have 5 html sources, in which I want to run readHTMLTable on each and store the result. I can do this individually using:

readHTMLTable(iso.content[1],which=6)
readHTMLTable(iso.content[2],which=6)
.
.

however when putting this into a for loop I get:

library(XML)
> iso.table<-NULL
> for (i in 1:nrow(gene.iso)) { 
+ iso.table[i]<-readHTMLTable(iso.content[i],which=6)
+ }
Warning messages:
1: In iso.table[i] <- readHTMLTable(iso.content[i], which = 6) :
  number of items to replace is not a multiple of replacement length
2: In iso.table[i] <- readHTMLTable(iso.content[i], which = 6) :
  number of items to replace is not a multiple of replacement length
3: In iso.table[i] <- readHTMLTable(iso.content[i], which = 6) :
  number of items to replace is not a multiple of replacement length
4: In iso.table[i] <- readHTMLTable(iso.content[i], which = 6) :
  number of items to replace is not a multiple of replacement length
5: In iso.table[i] <- readHTMLTable(iso.content[i], which = 6) :
  number of items to replace is not a multiple of replacement length

So I can do this individually, but not using a for loop. It is not my aim to replace the current data with the next iteration, so I am unsure why the warning presents this.

any ideas?

Answer 1

The error has nothing to do with readHTMLTable really; it's all about iso.table . I'm not sure what type of object you wanted that to be, but if you want to store a bunch of data.frames, you're going to need a list. And when you're assigning objects to a list, you want to place them with [[ ]] not [ ] . Try

iso.table <- list()
for (i in 1:nrow(gene.iso)) { 
    iso.table[[i]] <- readHTMLTable(iso.content[i],which=6)
}