Find the desired GA view ID for your API call with only the URL of the page going through GTM - the aim is mainly to avoid any search into your accounts especially if you have to many property IDs and all with the same site url

GAviewID_GTM_URL.R

library(httr)
library(XML)
library(googleAnalyticsR)
library(googleAuthR)

gwt_site_url <- "https://www.example.co.uk/"

html <- GET(gwt_site_url)

doc <- htmlParse(html)

attrs <- xpathApply(doc, "//iframe/@src")

gtm <- sapply(attrs, function(x) x[[1]])

gtm_value <- grep("GTM-", gtm, value = TRUE)

gtm_value <- gsub("https:|//www.googletagmanager.com/ns.html\\?id=", "", gtm_value)[1]

GTMhtml <- GET(paste0("https://www.googletagmanager.com/gtm.js?id=", gtm_value))

GTMdoc <- suppressWarnings(htmlParse(GTMhtml))

GTMattrs <- unlist(xpathApply(GTMdoc, "//p", xmlValue))

GAValue <- gsub("\\'.*","",gsub(".*UA-", "UA-",GTMattrs[2]))

gar_auth()

accounts <- ga_account_list()

accountsSite <- accounts[accounts$webPropertyId == GAValue,]

rownames(accountsSite) <- NULL

print(accountsSite)

n <- readline(prompt="Select view (row number): ")

GAviewID <- accountsSite$viewId[as.numeric(n)]