Datascraping to add to my existing offline dataframe with xml2 in R

Question

I am trying to scrape data from the IGRF Magnetic Model Calculator (https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml#igrfgrid) into a data frame that I already have that contains dates and lat/long. I only need two values from the calculator: total intensity and inclination.

My data frame looks like this (2012-2022; 24,000 observations):

UID	Animal ID	YEAR	Latitude	Longitude	Intensity	Inclination
1	C678	2012	30.98763	-80.98457	[add]	[add]
2	C679	2013	29.89765	-82.38304	[add]	[add]

Right now, I have my code running in a For loop to append these values to a list, but I am stuck on two main problems:

1. I would like this data to add to a new column to my data frame called “Intensity and “Inclination” so that is paired with my other observational data rather than in an empty list.

2. I am running into time out issues. The data frame I have has 20 columns and 24,000 rows, but my for loop stops running around entry 2,500. Is there a more efficient way to run this computation? (w/o a for-loop)

My code currently looks like this:

DF <- DF[which(!is.na(DF$Latitude) & !is.na(DF$Longitude)),]
Inclination<-list()
Intensity<-list()
base_url = "https://www.ngdc.noaa.gov/geomag-web/calculators/calculateIgrfwmm?"
for (i in 1:length(DF$UID)) {

full_url= paste0(base_url, "lat1=", DF$Latitude[i],
         "&lon1=",DF$Longitude[i], "&model=IGRF", "&startYear=", DF$Year[i], "&endYear=", DF$Year[i], "&key=EAU2y&resultFormat=xml")

dat <- read_xml(full_url)
xml_structure(dat) #how the xml is structured

dates <- as.numeric(xml_text(xml_find_all(dat, xpath = "//date")))
longs <- as.numeric(xml_text(xml_find_all(dat, xpath = "//longitude")))
lats <- as.numeric(xml_text(xml_find_all(dat, xpath = "//latitude")))
intensity_val <- as.numeric(xml_text(xml_find_all(dat, xpath = "//totalintensity")))
inclination_val <- as.numeric(xml_text(xml_find_all(dat, xpath = "//inclination")))

Intensity<-append(Intensity,intensity_val)
Inclination<-append(Inclination,inclination_val)

}