將行值與列名匹配並提取每列的最後一個值

...使用merge()或任何其他基本R函數。將行值與列名匹配並提取每列的最後一個值

例如，這裏有兩個數據幀：

V1 V2 V3 
1 DDPC 1747 57.19 
2 DDSG 1466 68.16 
3 DDG 2312 43.2 
4 DDL 2058 48.56 
5 DDUR 1779 56.14 
6 DDTH 1883 53.06 
7 DDAC 2020 49.47 

      DDG DDL DDO DDUR DDAC DDMG DDSG DDTH DDPC DDSUP 
2014-08-05 56.49 61.96 43.81 46.975 51.070 52.27 36.320 NA 1920.21 1364.44 
2014-08-06 56.40 61.88 43.50 46.860 50.850 52.01 36.305 NA 1920.24 1352.94 
2014-08-07 55.79 61.53 43.30 46.310 50.880 51.79 36.105 NA 1909.57 1343.21 
2014-08-08 56.29 61.71 43.78 46.530 50.800 52.27 36.545 NA 1931.59 1334.40 
2014-08-11 56.40 61.95 44.41 46.920 51.190 52.89 36.725 NA 1936.92 1352.42

我想有V4與對應的V1排列的最後一個值：

 V1 V2 V3 V4 
1 DDPC 1747 57.19 1936.92 
2 DDSG 1466 68.16 36.725 
3 DDG 2312 43.2 56.40 
4 DDL 2058 48.56 61.95 
5 DDUR 1779 56.14 46.92 
6 DDTH 1883 53.06 NA 
7 DDAC 2020 49.47 51.19

在this看了，但無法正確應用。

編輯 - 也有興趣從df1取V3列，並分配在df2的相應列名下匹配V1？

來源

2017-08-09 AK88

這是R.一個非常基本的操作只需'DF1 $ V4 < - 不公開（DF2 [nrow（DF2），as.character（df1 $ V1）]）'應該做 –

謝謝@DavidArenburg。通過申請我的意思是實施該主題中給出的建議。 – AK88

@DavidArenburg，我怎樣才能從'df1'中取出'V3'列，並在匹配'V1'的'df2'的相應列名下進行分配？ – AK88

嘗試此 -

dfa <- data.frame(V1 = letters[1:4], V2 = sample(10,4), V3 = sample(10,4)) 
dfb <- data.frame(a = sample(10,4),b = sample(10,4), c=sample(10,4), d=sample(10,4)) 
dfa['V4'] = unlist(sapply(dfa['V1'],function(x){dfb[nrow(dfb),x]}))

來源

2017-08-09 10:07:46

> dput(A) 
structure(list(V1 = c("DDPC", "DDSG", "DDG", "DDL", "DDUR", "DDTH", 
"DDAC"), V2 = c("1747", "1466", "2312", "2058", "1779", "1883", 
"2020"), V3 = c("57.19", "68.16", "43.2", "48.56", "56.14", "53.06", 
"49.47")), row.names = c(NA, -7L), .Names = c("V1", "V2", 
"V3"), class = "data.frame") 

> dput(B) 
structure(list(Date = c("2014-08-05", "2014-08-06", "2014-08-07", 
"2014-08-08", "2014-08-11"), DDG = c("56.49", "56.4", "55.79", 
"56.29", "56.4"), DDL = c("61.96", "61.88", "61.53", "61.71", 
"61.95"), DDO = c("43.81", "43.5", "43.3", "43.78", "44.41"), 
    DDUR = c("46.975", "46.86", "46.31", "46.53", "46.92"), DDAC = c ("51.07", 
"50.85", "50.88", "50.8", "51.19"), DDMG = c("52.27", "52.01", 
"51.79", "52.27", "52.89"), DDSG = c("36.32", "36.305", "36.105", 
"36.545", "36.725"), DDTH = c(NA_character_, NA_character_, 
NA_character_, NA_character_, NA_character_), DDPC = c("1920.21", 
"1920.24", "1909.57", "1931.59", "1936.92"), DDSUP = c("1364.44", 
"1352.94", "1343.21", "1334.4", "1352.42")), .Names = c("Date", 
"DDG", "DDL", "DDO", "DDUR", "DDAC", "DDMG", "DDSG", "DDTH", 
"DDPC", "DDSUP"), row.names = c(NA, -5L), class = "data.frame")

的代碼：

A[,"V4"]=unlist(B[nrow(B),match(A[,1],names(B))]) 
    A 
     V1 V2 V3  V4 
    1 DDPC 1747 57.19 1936.92 
    2 DDSG 1466 68.16 36.725 
    3 DDG 2312 43.2 56.4 
    4 DDL 2058 48.56 61.95 
    5 DDUR 1779 56.14 46.92 
    6 DDTH 1883 53.06 <NA> 
    7 DDAC 2020 49.47 51.19

來源

2017-08-09 11:23:21 Onyambu

將行值與列名匹配並提取每列的最後一個值

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