在数据框中找到最佳行

Question

我有一些包含某些位置的数据集:

ex <- data.frame(lat = c(55, 60, 40), long = c(6, 6, 10))

而且我有气候数据

clim <- structure(list(lat = c(55.047, 55.097, 55.146, 55.004, 55.054, 
55.103, 55.153, 55.202, 55.252, 55.301), long = c(6.029, 6.0171, 
6.0051, 6.1269, 6.1151, 6.1032, 6.0913, 6.0794, 6.0675, 6.0555
), alt = c(0.033335, 0.033335, 0.033335, 0.033335, 0.033335, 
0.033335, 0.033335, 0.033335, 0.033335, 0.033335), x = c(0, 0, 
0, 0, 0, 0, 0, 0, 0, 0), y = c(1914, 1907.3, 1901.8, 1921.1, 
1914.1, 1908.3, 1902.4, 1896, 1889.8, 1884)), row.names = c(NA, 
10L), class = "data.frame", .Names = c("lat", "long", "alt", 
"x", "y"))

      lat   long      alt x      y
1  55.047 6.0290 0.033335 0 1914.0
2  55.097 6.0171 0.033335 0 1907.3
3  55.146 6.0051 0.033335 0 1901.8
4  55.004 6.1269 0.033335 0 1921.1
5  55.054 6.1151 0.033335 0 1914.1
6  55.103 6.1032 0.033335 0 1908.3
7  55.153 6.0913 0.033335 0 1902.4
8  55.202 6.0794 0.033335 0 1896.0
9  55.252 6.0675 0.033335 0 1889.8
10 55.301 6.0555 0.033335 0 1884.0

我想要做的是"合并"两个数据集,以便在ex文件中包含气候数据.的价值lat和 long在ex比的值不同lat,并long在clim等我,他们不能直接合并(它是相同的long).我需要找到最好的点(在最近点clim的每一行中ex同时考虑lat和long)

该示例的预期输出是:

  lat long      alt x      y
1  55    6 0.033335 0 1914.0
2  60    6 0.033335 0 1884.0
3  40   10 0.033335 0 1921.1

Answer 1

您可以找到 中和中clim的绝对差值最小的行索引，然后根据该索引添加到列中。latlongexclimex

import(tidyverse)

ex %>%
  group_by(lat, long) %>%
  summarise(closest_clim = which.min(abs(lat - clim$lat) + 
                                       abs(long - clim$long))) %>%
  mutate(alt = clim$alt[closest_clim],
         x = clim$x[closest_clim],
         y = clim$y[closest_clim])

# A tibble: 3 x 6
# Groups:   lat [3]
    lat  long closest_clim    alt     x     y
  <dbl> <dbl>        <int>  <dbl> <dbl> <dbl>
1   40.   10.            4 0.0333    0. 1921.
2   55.    6.            1 0.0333    0. 1914.
3   60.    6.           10 0.0333    0. 1884.