Compute business days between two dates - r

Question

New to R and learning lot and I love it.
My sales dataset has product, bpid, date. I would like to calculate the business difference between same bpid (just excluding Saturday & Sunday) .
If product or bpid changes (Or new bpid/product introduced), we need to skip the computations.
df <- data.frame(product=c('milk','milk','milk','milk','eggs','eggs','eggs','eggs'),
bpid=c(400,400,500,500,400,400,500,500),
date=c("2016-08-03","2016-08-10","2016-08-04","2016-08-10","2016-08-10","2016-08-16","2016-08-11","2016-08-15"));
df$date <- as.Date(df$date, format = "%Y-%m-%d");
My Desired result would be like below. Please help....
product bpid date compute-result
milk 400 2016-08-03 0
milk 400 2016-08-10 5
milk 500 2016-08-04 0
milk 500 2016-08-10 5
eggs 400 2016-08-10 0
eggs 400 2016-08-16 4
eggs 500 2016-08-11 0
eggs 500 2016-08-15 2
Real Data code (getting zeros at result column)
df <- data.frame(product=c('Keyt','Keyt','Keyt','Keyt','Keyt','Keyt'),
bpid=c(30057,30057,30057,30058,30058,30058),
date=c("2014-11-21","2015-05-05","2015-05-11","2014-10-16","2014-11-03","2016-03-15"));
df$date <- as.Date(df$date, format = "%Y-%m-%d");
cal <- Calendar(weekdays=c("saturday", "sunday"))
df$`compute-result` <- 0
idx <- seq(1, nrow(df),2)
df$`compute-result`[idx+1] <- bizdays(df$date[idx], df$date[idx+1], cal)
df

Answer 1

For example:
# install.packages("bizdays")
library(bizdays)
cal <- create.calendar(name = "mycal", weekdays=c("saturday", "sunday"))
df$`compute-result` <- 0
idx <- seq(1, nrow(df),2)
df$`compute-result`[idx+1] <- bizdays(df$date[idx], df$date[idx+1], cal)
df
# product bpid date compute-result
# 1 milk 400 2016-08-03 0
# 2 milk 400 2016-08-10 5
# 3 milk 500 2016-08-04 0
# 4 milk 500 2016-08-10 4
# 5 eggs 400 2016-08-10 0
# 6 eggs 400 2016-08-16 4
# 7 eggs 500 2016-08-11 0
# 8 eggs 500 2016-08-15 2
if you want to group by product and bpid, you could try
# install.packages("bizdays")
library(bizdays)
cal <- create.calendar(name="mycal", weekdays=c("saturday", "sunday"))
with(df, ave(as.integer(date), product, bpid, FUN=function(x) {
x <- as.Date(x, origin="1970-01-01")
c(0, bizdays(head(x, -1), tail(x, -1), cal))
})) -> df$result
df
# product bpid date result
# 1 Keyt 30057 2014-11-21 0
# 2 Keyt 30057 2015-05-05 117
# 3 Keyt 30057 2015-05-11 4
# 4 Keyt 30058 2014-10-16 0
# 5 Keyt 30058 2014-11-03 12
# 6 Keyt 30058 2016-03-15 356
Note that is converted date to integer and back to Date inside the function because otherwise ave throws an error:
Error in as.Date.numeric(value) : 'origin' must be supplied
and I dunno how to supply that origin argument here.