Dear all,
this is a basic question but I could not find a specific answer online.
I have a dataframe (df1) with, in particular, an identification value
`x` and an output value `z`.
I also have another dataframe (df2) that shares `x`.
I need to assign `z` to df2 where df1$x is equal to df2$x.
What would be a straightforward way of doing this?
I can do it, but selecting one element at a time, checking the
identity of the x elements, and then assigning z. There should be a
more R way...
Thank you
```
df1 = data.frame(x = 1:20,
y = rep(letters[1:5],4),
w = c(rep(LETTERS[1],10), rep(LETTERS[2],10)),
z = rnorm(20),
stringsAsFactors = FALSE)
df2 = data.frame(x = sample(df1$x, 5))
df2$z = NA
for (i in df1$x) {
df2$z[df2$x==i] = df1[df1$x==i,]$z
}
```
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