r中列之间的线性插值

Question

我正在处理一些温度数据，其中我有特定深度的温度，例如0.9m、2.5m 和 5m。我想对这些值进行插值，以便获得每米的温度，例如1 米、2 米和 3 米。原始数据如下所示：

df
# A tibble: 5 x 3
  date                d_0.9 d_2.5  
  <dttm>              <dbl> <dbl> 
1 2004-01-05 03:00:00  7     8        
2 2004-01-05 04:00:00  7.5   9      
3 2004-01-05 05:00:00  7     8        
4 2004-01-05 06:00:00  6.92  NA

我想得到的是这样的：

df_int
# A tibble: 5 x 5
  date                 d_0.9   d_1      d_2      d_2.5  
  <dttm>              <dbl>   <dbl>     <dbl>    <dbl>
1 2004-01-05 03:00:00  7       7.0625   7.6875   8     
2 2004-01-05 04:00:00  7.5     7.59375  8.53125  9      
3 2004-01-05 05:00:00  7       7.0625   7.6875   8  
4 2004-01-05 06:00:00  6.92    NA       NA       NA

我必须对非常大的数据框执行此操作。有没有有效的方法？

非常感谢

Answer 1

一个选项是将数据转换为长格式，使用连接为我们想要插值的深度添加行，然后使用 approx 进行插值：

library(tidyverse)

# Data
df = tibble(date=seq(as.POSIXct("2004-01-05 03:00:00"),
                     as.POSIXct("2004-01-05 06:00:00"),
                     by="1 hour"),
            d_0.9 = c(7,7.5,7,6.92),
            d_2.5 = c(8,NA,8,NA),
            d_5.0 = c(10,10.5,9.4,NA))

# Create a data frame with all of the times and depths we want to interpolate at
depths = sort(unique(c(c(0.9, 2.5, 5), seq(ceiling(0.9), floor(5), 1))))
depths = crossing(date=unique(df$date), depth = depths)

# Convert data to long format, join to add interpolation depths, then interpolate
df.interp = df %>% 
  gather(depth, value, -date) %>% 
  mutate(depth = as.numeric(gsub("d_", "", depth))) %>% 
  full_join(depths) %>% 
  arrange(date, depth) %>% 
  group_by(date) %>% 
  mutate(value.interp = if(length(na.omit(value)) > 1) {
    approx(depth, value, xout=depth)$y
  } else {
    value
  })

在上面的代码中，包含 if 语句以防止 approx 在给定的 date 只有一个非缺失值时抛出错误。

df.interp

                  date depth value value.interp
1  2004-01-05 03:00:00   0.9  7.00     7.000000
2  2004-01-05 03:00:00   1.0    NA     7.062500
3  2004-01-05 03:00:00   2.0    NA     7.687500
4  2004-01-05 03:00:00   2.5  8.00     8.000000
5  2004-01-05 03:00:00   3.0    NA     8.400000
6  2004-01-05 03:00:00   4.0    NA     9.200000
7  2004-01-05 03:00:00   5.0 10.00    10.000000
8  2004-01-05 04:00:00   0.9  7.50     7.500000
9  2004-01-05 04:00:00   1.0    NA     7.573171
10 2004-01-05 04:00:00   2.0    NA     8.304878
11 2004-01-05 04:00:00   2.5    NA     8.670732
12 2004-01-05 04:00:00   3.0    NA     9.036585
13 2004-01-05 04:00:00   4.0    NA     9.768293
14 2004-01-05 04:00:00   5.0 10.50    10.500000
15 2004-01-05 05:00:00   0.9  7.00     7.000000
16 2004-01-05 05:00:00   1.0    NA     7.062500
17 2004-01-05 05:00:00   2.0    NA     7.687500
18 2004-01-05 05:00:00   2.5  8.00     8.000000
19 2004-01-05 05:00:00   3.0    NA     8.280000
20 2004-01-05 05:00:00   4.0    NA     8.840000
21 2004-01-05 05:00:00   5.0  9.40     9.400000
22 2004-01-05 06:00:00   0.9  6.92     6.920000
23 2004-01-05 06:00:00   1.0    NA           NA
24 2004-01-05 06:00:00   2.0    NA           NA
25 2004-01-05 06:00:00   2.5    NA           NA
26 2004-01-05 06:00:00   3.0    NA           NA
27 2004-01-05 06:00:00   4.0    NA           NA
28 2004-01-05 06:00:00   5.0    NA           NA

r中列之间的线性插值

Linear interpolation among columns in r

interpolation

r