library(osmdata)
library(sf)
library(sfheaders)
library(geosphere)

getmindist<-function(x1,y1,x2,y2){
	tav <- distm(data.frame(x1,y1),data.frame(x2,y2))
	apply(tav,1,min, simplify = T)
}

metro <- getbb("Budapest") %>%
	opq() %>%
	add_osm_feature("station","subway") %>%
	osmdata_sf()

metro <- data.frame(metro$osm_points)

metro$lat <- sapply(metro$geometry, unlist)[2,]
metro$lon <- sapply(metro$geometry, unlist)[1,]

vonat <- getbb("Budapest") %>%
		opq()%>%
		add_osm_feature(c("railway","train"),c("station","yes"))%>%
		osmdata_sf()

vonat <- vonat$osm_points

vonat$lat <- sapply(vonat$geometry,unlist)[2,]
vonat$lon <- sapply(vonat$geometry,unlist)[1,]

df$metrotav <- getmindist(df$lon,df$lat,metro$lon,metro$lat)
df$vonattav <- getmindist(df$lon,df$lat,vonat$lon,vonat$lat)

df$tomkoz <- apply(df[,c("vonattav","metrotav")],1,min, simplify = T)