CODEWITHSUNDEEP
rdplyr
MAOC
MAOC

Reputation: 635

In R, use dplyr functions to find minimum distance

I have a dataframe with two numeric variables: lat and long. Something like this

> head(pontos_sub)
  id       lat      long
1  0 -22,91223 -43,18810
2  1 -22,91219 -43,18804
3  2 -22,91225 -43,18816
4  3 -22,89973 -43,20855
5  4 -22,89970 -43,20860
6  5 -22,89980 -43,20860

Now, I will do a round number:

pontos_sub$long_r <- round(pontos_sub$long, 3)
pontos_sub$lat_r <- round(pontos_sub$lat, 3)

> head(pontos_sub)
  id       lat      long  long_r   lat_r
1  0 -22,91223 -43,18810 -43,188 -22,912 
2  1 -22,91219 -43,18804 -43,188 -22,912
3  2 -22,91225 -43,18816 -43,188 -22,912
4  3 -22,89973 -43,20855 -43,209 -22,900 
5  4 -22,89970 -43,20860 -43,209 -22,900
6  5 -22,89980 -43,20860 -43,209 -22,900

Now, I would like to use dplyr to find, grouped by each unique long_r lat_r and using the distVincentyEllipsoid function, the minimum distance to all lat long of the corresponding group. 

> newdata <- pontos_sub %>% 
               group_by(long_r,lat_r) %>% 
               summarise(min_long = special_fun(arg), 
                         min_lat = special_fun(arg))

Resulting something like this:

> head(newdata)
  long_r   lat_r   min_long  min_lat
1 -43,188 -22,912   xxxxxx   xxxxxxx
4 -43,209 -22,900   xxxxxx   xxxxxxx

Finally, Is this the fast way? Or Is there other way more fast? T

Upvotes: 0

Views: 181

Answers (1)

Scarabee
Scarabee

Reputation: 5704

You can do it this way:

pontos_sub %>% 
  mutate(dist = distVincentyEllipsoid(cbind(long, lat), cbind(long_r, lat_r))) %>% 
  group_by(long_r, lat_r) %>% 
  arrange(dist) %>% 
  slice(1) %>% 
  rename(min_long = long, min_lat = lat) %>% 
  select(long_r, lat_r, min_long, min_lat)

# Source: local data frame [2 x 4]
# Groups: long_r, lat_r [2]
# 
#    long_r   lat_r  min_long   min_lat
#     <dbl>   <dbl>     <dbl>     <dbl>
# 1 -43.209 -22.900 -43.20860 -22.89980
# 2 -43.188 -22.912 -43.18804 -22.91219

Data:

pontos_sub <- read.table(text="
  id       lat      long
1  0 -22,91223 -43,18810
2  1 -22,91219 -43,18804
3  2 -22,91225 -43,18816
4  3 -22,89973 -43,20855
5  4 -22,89970 -43,20860
6  5 -22,89980 -43,20860                
                ", dec = ",")

pontos_sub$long_r <- round(pontos_sub$long, 3)
pontos_sub$lat_r <- round(pontos_sub$lat, 3)

Upvotes: 1

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