CODEWITHSUNDEEP
rselectfilterdplyr
Arpit Goel
Arpit Goel

Reputation: 163

R filter rows : where clause : from dataframe

I am trying to filter a dataframe in R as follows.

Let mydf be the dataframe having two columns A and B.

Let udf be another dataframe having 1 column A.

I want to do the following.

Select rows from mydf where mydf[A] is in udf[A]

I am using dplyr and tried something on the lines as 

T = filter(mydf, A %in% udf['A'])

That clearly doesn't work. Is there a straightforward workaround for this without explicitly writing for loop ? Thanks a lot!

Upvotes: 3

Views: 4730

Answers (2)

akrun
akrun

Reputation: 887163

You could use inner_join from dplyr

library(dplyr)
r1 <- inner_join(mydf, udf, by='A')

Or using filter as commented by @BondedDust 

r2 <- filter(mydf, A %in% udf[['A']])
identical(r1, r2)
#[1] TRUE

Or using data.table

library(data.table)
setkey(setDT(mydf),A)[udf, nomatch=0]

data

set.seed(24)
mydf <- as.data.frame(matrix(sample(1:10,2*10, replace=TRUE),
    ncol=2, dimnames=list(NULL, LETTERS[1:2])) )
set.seed(29)
udf <- data.frame(A=sample(1:10,6,replace=TRUE))

Upvotes: 2

daniel
daniel

Reputation: 1246

You can simply pip data and use the left_join function. Here is a reproducible example for this:

Data:

set.seed(123)
colors<- c( rep("yellow", 5), rep("blue", 5), rep("green", 5) )
shapes<- c("circle", "star", "oblong")
numbers<-sample(1:15,replace=T)
group<-sample(LETTERS, 15, replace=T)
mydf<-data.frame(colors,shapes,numbers,group)
mydf

mydf2<- mydf %>%  
    filter (colors=="yellow")

 mydf3 <- mydf %>% left_join(mydf2)

Upvotes: 0

Related Questions