r - How to select rows from data.frame with 2 conditions

Question

I have an aggregated table:

> aggdata[1:4,]
  Group.1 Group.2         x
1       4    0.05 0.9214660
2       6    0.05 0.9315789
3       8    0.05 0.9526316
4      10    0.05 0.9684211

How can I select the x value when I have values for Group.1 and Group.2?

I tried:

aggdata[aggdata[,"Group.1"]==l && aggdata[,"Group.2"]==lamda,"x"]

but that replies all x's.

More info: I want to use this like this:

table = data.frame();
for(l in unique(aggdata[,"Group.1"])) {
    for(lambda in unique(aggdata[,"Group.2"])) {
        table[l,lambda] = aggdata[aggdata[,"Group.1"]==l & aggdata[,"Group.2"]==lambda,"x"]
    }
}

Any suggestions that are even easier and giving this result I appreciate!

Answer 1

The easiest solution is to change "&&" to "&" in your code.

> aggdata[aggdata[,"Group.1"]==6 & aggdata[,"Group.2"]==0.05,"x"]
[1] 0.9315789

My preferred solution would be to use subset():

> subset(aggdata, Group.1==6 & Group.2==0.05)$x
[1] 0.9315789