i have dt , desire compute easy stock balances shown. computations easy , immediate in excel, allows recursive computations.
library(data.table) dt <- data.table(expand.grid(8:9, 0:59, 1:4)) names(dt) <- c("hour", "minute", "shop") set.seed(1234) dt <- dt[, ':=' (demand = rpois(1, lambda = 0.8), stock_in = rpois(1, lambda = 0.05)*250 ), by=names(dt)] dt$stock_before <- na dt$stock_after <- na dt$sells <- na dt$lost_sells <- na dt$stock_before[which(dt$hour == 8 & dt$minute == 0)] <- c(21, 45, 31, 50) dt <- dt[order(dt$hour, dt$minute, dt$shop),] the desired format done, using tapply slow. tried use data table syntax better.
since stock_before of minute stock_after of minute before, line designed reports error. command use following lines:
dt <- dt[, ':=' ( stock_after = max(0, stock_before+stock_in-demand), stock_before = shift(stock_after, 1), sells = min(stock_before + stock_in, demand, na.rm=t), lost_sells = max(demand-sells, 0) ), by=shop] and error following:
error in shift(stock_after, 1) : object 'stock_after' not found in addition: warning message: in `[.data.table`(dt, , `:=`(stock_after = max(0, stock_before + : invalid .internal.selfref detected , fixed taking (shallow) copy of data.table := can add new column reference. @ earlier point, data.table has been copied r (or been created manually using structure() or similar). avoid key<-, names<- , attr<- in r (and oddly) may copy whole data.table. use set* syntax instead avoid copying: ?set, ?setnames , ?setattr. also, in r<=v3.0.2, list(dt1,dt2) copied entire dt1 , dt2 (r's list() used copy named objects); please upgrade r>v3.0.2 if biting. if message doesn't help, please report datatable-help root cause can fixed. the results show below:
head(dt, 12) hour minute shop demand stock_in stock_before stock_after sells lost_sells 1 8 0 1 0 0 21 21 0 0 2 8 0 2 0 0 45 45 0 0 3 8 0 3 1 0 31 30 1 0 4 8 0 4 2 0 50 48 2 0 5 8 1 1 2 0 21 19 2 0 6 8 1 2 3 0 45 42 3 0 7 8 1 3 0 0 30 30 0 0 8 8 1 4 1 250 48 297 1 0 9 8 2 1 1 0 19 18 1 0 10 8 2 2 3 0 42 39 3 0 11 8 2 3 1 0 30 29 1 0 12 8 2 4 0 250 297 547 0 0 can me? lot!
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