Scraping data from finviz with R - Structure for - r

Question

I am new using R and this is my first question. I apologize if it has been solved before but I haven't found a solution.
By using below code, that I found here, I can get data from and specific subsector from Finviz screener:
library (rvest)
url <- read_html("https://finviz.com/screener.ashx?v=111&f=geo_usa,ind_specialtyindustrialmachinery&o=industry")
tables <- html_nodes(url,"table")
screener <- tables %>% html_nodes("table") %>% .[11] %>%
html_table(fill=TRUE) %>% data.frame()
head(screener)
It was a bit difficult to find the table number bud I did. My question refers to lists with more than 20, like the one I am using at the example. They use &r=1, &r=21, &r=41, &r=61 at the end of each url.
How could I create in this case the structure?
i=0
for(z in ...){
Many thanks in advance for your help.

Answer 1

Update script based on new table number and link:
library (rvest)
library(stringr)
url <- "https://finviz.com/screener.ashx?v=111&f=geo_usa,ind_specialtyindustrialmachinery&o=industry"
TableList<-c("1","21","41","61") # table list
GetData<-function(URL,tableNo){
cat('\n',"Running For table",tableNo,'\n', 'Weblink Used:',stringr::str_c(url,"&r=",tableNo),'\n')
tables<-read_html(stringr::str_c(url,"&r=",tableNo)) #get data from webpage based on table numbers
screener <- tables %>%
html_nodes("table") %>%
.[17] %>%
html_table(fill=TRUE) %>%
data.frame()
return(screener)
}
AllData<- lapply(TableList, function(x) GetData(URL=url, tableNo = x)) # getting all data in form of list
Here is one approach using stringr and lapply:
library (rvest)
library(stringr)
url <- "https://finviz.com/screener.ashx?v=111&f=geo_usa,ind_specialtyindustrialmachinery&o=industry" # base url
TableList<-c("1","21","41","61") # table number list
GetData<-function(URL,tableNo){
cat('\n',"Running For table",tableNo,'\n', 'Weblink Used:',stringr::str_c(url,"&",tableNo),'\n')
tables<-read_html(stringr::str_c(url,"&",tableNo)) #get data from webpage based on table numbers
screener <- tables %>%
html_nodes("table") %>%
.[11] %>% # check
html_table(fill=TRUE) %>%
data.frame()
return(screener)
}
AllData<- lapply(TableList, function(x) GetData(URL=url, tableNo = x)) # list of dataframes
However please check for .[11] number as it will be changed for these URLs(URL with &1, &21, etc). It is working fine for the base URL. Data is not present for the URL with &1, &21, etc at 11th index. Please change accordingly.