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Conditional duplication

Given the following data frame:

   z1 z2
1   A  X
2   A  Y
3   B  X
4   B  Y
5   C  X
6   C  Z
7   D  X
8   D  Z
9   E  X
10  E  Y
11  F  X
12  G  Z
13  H  X
14  I  Y
15  J  X
16  K  Z

I am trying to find a more efficient (than I came) way of eliminating duplicate values ​​in the first column, z1, given the value in the second column z2, is not the specified value "X". This is the result that I get after:

   z1 z2
1   A  X
3   B  X
5   C  X
7   D  X
9   E  X
11  F  X
12  G  Z
13  H  X
14  I  Y
15  J  X
16  K  Z

( ) , duplicated() unique(), , , , . , , , z1, z2, z2 , z1 , , subset(), , z1, , . , , .

, :

z1=c(rep(c("A","B","C","D","E"),each=2),"F","G","H","I","J","K")
z2=c(rep(c("X","Y"),2),rep(c("X","Z"),2),rep(c("X","Y","X","Z"),2))
z=data.frame(cbind(z1,z2))

t1=subset(z, 
    (z$z1!="A" | z$z2=="X")&
    (z$z1!="B" | z$z2=="X")&
    (z$z1!="C" | z$z2=="X")&
    (z$z1!="D" | z$z2=="X")&
    (z$z1!="E" | z$z2=="X"))
t1

?

+3
4

duplicated, fromLast=F fromLast=T, , z1:

duplicated(z$z1) | duplicated(z$z1, fromLast=T)
#  [1]  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE  TRUE FALSE FALSE FALSE
# [14] FALSE FALSE FALSE

, , X2 "X":

subset(z, !(duplicated(z1) | duplicated(z$z1, fromLast=T)) | z2 == "X")
#    z1 z2
# 1   A  X
# 3   B  X
# 5   C  X
# 7   D  X
# 9   E  X
# 11  F  X
# 12  G  Z
# 13  H  X
# 14  I  Y
# 15  J  X
# 16  K  Z
+3

?

> wh = with(DF, match(unique(z1),z1))
> DF[wh,]
 z1 z2
1   A  X
3   B  X
5   C  X
7   D  X
9   E  X
11  F  X
12  G  Z
13  H  X
14  I  Y
15  J  X
16  K  Z
+1
z[!(duplicated(z$z1) | duplicated(z$z1, fromLast = TRUE) & z$z2 != "X"),]

##    z1 z2                                                                                                                                                                                                                                   
## 1   A  X                                                                                                                                                                                                                                   
## 3   B  X                                                                                                                                                                                                                                   
## 5   C  X                                                                                                                                                                                                                                   
## 7   D  X                                                                                                                                                                                                                                   
## 9   E  X                                                                                                                                                                                                                                   
## 11  F  X                                                                                                                                                                                                                                   
## 12  G  Z                                                                                                                                                                                                                                   
## 13  H  X                                                                                                                                                                                                                                   
## 14  I  Y                                                                                                                                                                                                                                   
## 15  J  X                                                                                                                                                                                                                                   
## 16  K  Z
+1
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This is actually pretty easy.

Creating a data frame:

df <- read.table(text="  z1 z2
1   A  X
2   A  Y
3   B  X
4   B  Y
5   C  X
6   C  Z
7   D  X
8   D  Z
9   E  X
10  E  Y
11  F  X
12  G  Z
13  H  X
14  I  Y
15  J  X
16  K  Z", stringsAsFactors=FALSE)

Now

t1<-df[!duplicated(df$z1),]

This will give you:

  z1 z2
1   A  X
3   B  X
5   C  X
7   D  X
9   E  X
11  F  X
12  G  Z
13  H  X
14  I  Y
15  J  X
16  K  Z
0
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