R help - Sep 2013 - Intersect 2 lists+bring extra columns

Hi everyone,

I am pretty new to R, so be patient. 

I am trying to intersect 2 columns and in the rows that intersect, I want
information from the 3rd column to be brought with it. I think it will be
easier to explain with an example  example.csv
<http://r.789695.n4.nabble.com/file/n4675136/example.csv>  . 

In my example, I have a reference list of fruit (first column), and my fruit
of interest (second column), and then in the third column, I have color
information about the fruit of interest in the second column. 

Currently to find the intersection between column 1 and 2, I use
>fruit<-read.csv("//Users//J//Desktop//example.csv",
header=TRUE)
>output<-intersect(fruit[,1],fruit[,2])
>write.table(data.frame(fruit),"output.xls", col.names=TRUE,
row.names=FALSE)

However, it would save me a lot of time if I could have the color
information from column 3 be saved with the overlap. I normally have
reference list of several hundred and lists of interest in the several
thousand, and bringing over the information column would be hard manually.

Is there some sort of If function I could be using? I would really like
something like If row x, column 2 intersects with row x, column 1, then row
x column 3 is stored with it. I can think through the logic, but not sure
how to do it in R. 

Any help would be much appreciated!



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HI,

If I understand it correctly:

fruit<-
read.csv("example.csv",header=TRUE,stringsAsFactors=FALSE,sep="\t")
?res<-merge(fruit["reference"],fruit[,-1],by.x="reference",by.y="list")
?res
#?? reference information
#1 grapefruit??????? pink
#2????? lemon????? yellow
#3?????? pear?????? green

If the dataset have duplicate entries in the second and third columns.? For
example:
?fruit1<- fruit
?fruit1[4,2]<- "lemon"
fruit1[4,3]<- "yellow"
?res2<-
merge(fruit1["reference"],fruit1[,-1],by.x="reference",by.y="list")
res2
#?? reference information
#1 grapefruit??????? pink
#2????? lemon????? yellow
#3????? lemon????? yellow
#4?????? pear?????? green

unique(res2)
#?? reference information
#1 grapefruit??????? pink
#2????? lemon????? yellow
#4?????? pear?????? green
A.K.



Hi everyone, 

I am pretty new to R, so be patient. 

I am trying to intersect 2 columns and in the rows that 
intersect, I want information from the 3rd column to be brought with it.
 I think it will be easier to explain with an example example.csv. 

In my example, I have a reference list of fruit (first column), 
and my fruit of interest (second column), and then in the third column, I
 have color information about the fruit of interest in the second 
column. 

Currently to find the intersection between column 1 and 2, I use
>fruit<-read.csv("//Users//J//Desktop//example.csv",
header=TRUE)
>output<-intersect(fruit[,1],fruit[,2]) 
>write.table(data.frame(fruit),"output.xls", col.names=TRUE,
row.names=FALSE)
However, it would save me a lot of time if I could have the 
color information from column 3 be saved with the overlap. I normally 
have reference list of several hundred and lists of interest in the 
several thousand, and bringing over the information column would be hard
 manually. 

Is there some sort of If function I could be using? I would 
really like something like If row x, column 2 intersects with row x, 
column 1, then row x column 3 is stored with it. I can think through the
 logic, but not sure how to do it in R. 

Any help would be much appreciated!