I have a dataframe "old_df" and I would like to refer to its columns with "i" in a for loop and do some operations (the operation below is only an example).
v1 <- c(1,2,3)
v2 <- c(4,5,6)
old_df = data.frame(Price=v1, Value=v2)
colnames = c("Price", "Value")
new_df = data.frame(Price=numeric(),
Value=numeric())
for (i in colnames) {
new_df$i <- old_df$i
}
However referencing this way (old_df$i) does not work. Writing old_df$"Price" into the console gives back the correct column, writing i gives back label "Price", however old_df$i gives back NULL. What is the problem here?
