條件匹配/合併中的R

Question

我有不等數量的行的兩個數據幀：

df1 

Label Country Year 
NU  Germany 1999 
BU  Italy  1945 
LU  France  2009 
KM  Sweden  1998 
NU  Germany 1999 

和

df2 

Make  Label  
X1  NU 
X2  BU 
X3  NU 
X4  NU 
X5  KM 

我想什麼做的是「標籤」的比賽，並最終有以下幾點：

Make Label Country  Year 
X1  NU  Germany  1999 
X2  BU  Italy  1945 
X3  NU  Germany  1999 
X4  NU  Germany  1999 
X5  KM  Sweden  1998 

Answer 1

a=merge(df2,df1,by="Label") 
a[!duplicated(a),] 
    Label Make Country Year 
1 BU X2 Italy 1945 
2 KM X5 Sweden 1998 
3 NU X1 Germany 1999 
5 NU X3 Germany 1999 
7 NU X4 Germany 1999