Subset a data frame based on matching columns to rows - R

Question

I am trying to subset a large data frame based on matching IDs from another data frame. I read the answer to this question posted:

R: subset a data frame based on conditions from another data frame

However, my data differs from this in that for one of my data sets I have the linker ID set up in a column, and in the other, it goes across rows

Data set 1

*ID* time stat
*1* 3.21 6
*4* 7.9 3
...

Data set 2

*ID 1 2 4* ...
y yellow brown yellow
z 3 5 2
a yes yes no

What I ultimately would like to get is a data frame where I only have the data from data set 2 that has a matching sample ID in data set 1. So in this example:

*ID 1 4* ...
y yellow yellow
z 3 2
a yes no

Any help is much appreciated.

Andrea

Answer 1

all you need to do is

newDf<-df2[,df2[1,]%in%df1[,1]]

where df1[,1] is the data set with the id column in column position 1, and df2[1,] is the dataset with the id column in row position 1.

df2[1,]
#[1] 1 3 4

df1[,1]
#[1] 1 4

df2[1,]%in%df1[,1]
#[1] TRUE FALSE TRUE