Compare two data frames with different rows using R

Question

I have two data frames with different row numbers:

class1<-c(1,2,5,6,7)
abund1<-c(10.4,7.5,7.1,5.1,3.2)
df1<-data.frame(class1,abund1)

class2<-c(1,2,3,4,5,6,7)
abund2<-c(9.5,8.4,8,6.3,6,2.4,1.2)
df2<-data.frame(class2,abund2)

I would like to compare these two data frames but I would need the same number of rows. My purpose is to fill by zero all those classes which do not match with the df2. The solution would be as it follows:

  class abund
     1   10.4
     2    7.5
     3    0.0
     4    0.0
     5    7.1
     6    5.1
     7    3.2

Any ideas? Thank you so much!

I tried to use the merge function but I don't know how to fill the empty classes by 0. — Rinot
– Rinot, Commented Jul 6, 2015 at 3:30

user227710 · Accepted Answer · 2015-07-06 03:32:33Z

1

kk<-merge(df1,df2,by.x="class1",by.y="class2",all.y=TRUE)[-3]
kk[is.na(kk$abund1),2]<-0
> kk
  class1 abund1
1      1   10.4
2      2    7.5
3      3    0.0
4      4    0.0
5      5    7.1
6      6    5.1
7      7    3.2

answered Jul 6, 2015 at 3:32

user227710

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1 Comment

Rinot Over a year ago

Thank you for your quick and rigth answer @user227710!

akrun · Accepted Answer · 2015-07-06 06:43:28Z

0

An option with data.table

 library(data.table)#v1.9.5+
 setDT(df1, key='class1')[df2][is.na(abund1), abund1:=0][, abund2:=NULL][]
 #   class1 abund1
 #1:      1   10.4
 #2:      2    7.5
 #3:      3    0.0
 #4:      4    0.0
 #5:      5    7.1
 #6:      6    5.1
 #7:      7    3.2

answered Jul 6, 2015 at 6:43

akrun

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