Minus operation of data frames

Question

I have 2 data frames df1 and df2.

df1 <- data.frame(c1=c(\"a\",\"b\",\"c\",\"d\"),c2=c(1,2,3,4) )
df2 <- data.frame(c1=c(\"         


        

Answer 1

You can create identifier columnas then subset:

e.g.

df1 <- data.frame(c1=c("a","b","c","d"),c2=c(1,2,3,4), indf1 = rep("Y",4) )
df2 <- data.frame(c1=c("c","d","e","f"),c2=c(3,4,5,6),indf2 = rep("Y",4) )
merge(df1,df2)
#  c1 c2 indf1 indf2
#1  c  3     Y     Y
#2  d  4     Y     Y

bigdf <- merge(df1,df2,all=TRUE)
#  c1 c2 indf1 indf2
#1  a  1     Y  
#2  b  2     Y  
#3  c  3     Y     Y
#4  d  4     Y     Y
#5  e  5       Y
#6  f  6       Y

Then subset how you wish:

 bigdf[is.na(bigdf$indf1) ,]
#  c1 c2 indf1 indf2
#5  e  5       Y
#6  f  6       Y

 bigdf[is.na(bigdf$indf2) ,]  #<- output you requested those not in df2
#  c1 c2 indf1 indf2
#1  a  1     Y  
#2  b  2     Y