Hi,
Try:
indx <- as.vector(with(dat,tapply(seq_along(price), list(id), FUN= head,1)))
dat$adjusted_price <- dat$price
dat$adjusted_price[indx] <- with(dat, price[indx]-adj_factor[indx])
dat
# key id price adj_factor adjusted_price
#1 A instru_A 101.3800 2.0800 99.3000
#2 B instru_B 3.9306 2.5217 1.4089
#3 C instru_B 3.7488 2.5217 3.7488
#4 D instru_B 92.9624 2.5217 92.9624
#5 E instru_C 5.1500 3.0800 2.0700
#6 E instru_C 96.1908 3.0800 96.1908
A.K.
Dear R forum I have following data.frame dat = data.frame(key = c("A", "B",
"C", "D", "E", "E"), id = c("instru_A", "instru_B", "instru_B", "instru_B",
"instru_C", "instru_C"), price = c(101.38, 3.9306, 3.7488, 92.9624, 5.15,
96.1908), adj_factor = c(2.08, 2.5217, 2.5217, 2.5217, 3.08, 3.08)) > dat key
id price adj_factor
1 A instru_A 101.3800 2.0800
2 B instru_B 3.9306 2.5217
3 C instru_B 3.7488 2.5217
4 D instru_B 92.9624 2.5217
5 E instru_C 5.1500 3.0800
6 E instru_C 96.1908 3.0800 This is just a part of big database and ids
can appear any no of times. # MY PROBLEM I need to subtract adj_factor from the
price, however only from the first id only. In case of instru_A, there is only
1 id, so 2.08 should be subtracted from 101.38. The id "instru_B" is appearing
3 times. So in this case, adj_factor = 2.5217 should be subtracted from 3.9306
and rest should remain same. Similarly, id "instru_C" is appearing 2 times,
hence the adj_factor = 3.08 should be subtracted from 5.15. Effectively I am
looking for > dat_new key id price adj_factor
adjusted_price
1 A instru_A 101.3800 2.0800 99.3000 # price adjusted
2 B instru_B 3.9306 2.5217 1.4089 # price adjusted
3 C instru_B 3.7488 2.5217 3.7488
4 D instru_B 92.9624 2.5217 92.9624
5 E instru_C 5.1500 3.0800 2.0700 # price adjusted
6 E instru_C 96.1908 3.0800 96.1908 I tried something like
adj_price = function(id, price, adj_factor)
{
id_length = length(id) if(id_length == 1) {
(adjusted_price = price-adj_factor)
} if(id_length == 2) {
(adjusted_price = c(price[1]-adj_factor[1], price[2]))
} if(id_length > 2) {
(adjusted_price = c(price[1]-adj_factor[1],price[2:id_length]))
} return(adjusted_price) } (final_price = adj_price(dat$id, dat$price,
dat$adj_factor)) > (final_price = adj_price(dat$id, dat$price, dat$adj_factor))
[1] 99.3000 3.9306 3.7488 92.9624 5.1500 96.1908 Kindly advise Regards
Katherine
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