在另一列中找到的汇总列的R总和

Question

Given this data, the first 4 columns (rowid, order, line, special), I need to create a column, numSpecial as such:

rowid   order    line    special    numSpecial
1       A        01      X          1
2       B        01                 0
3       B        02      X          2
4       B        03      X          2
5       C        01      X          1
6       C        02                 0

Where numSpecial is determined by summing the number of times for each order that is special (value = X), given that order-line is special itself, otherwise its 0.

I first tried adding a column that simply concats 'order' with 'X', call it orderX, and would look like:

orderX
AX
BX
BX
BX
CX
CX

Then do a sum of order & special in orderx:

df$numSpecial <- sum(paste(order, special, sep = "") %in% orderx)

But that doesnt work, it returns the sum of the results for all rows for every order:

numSpecial
4
4
4
4
4
4

I then tried as.data.table, but I'm not getting the expected results using:

as.data.table(mydf)[, numSpecial := sum(paste(order, special, sep = "") %in% orderx), by = rowid]

However that is returning just 1 for each row and not sums:

numSpecial
1
0
1
1
1
0

Where am I going wrong with these? I shouldn't have to create that orderX column either I don't think, but I can't figure out the way to get this count right. It's similar to a countif in excel which is easy to do.

Answer 1

There's probably several ways, but you could just multiply it by a TRUE/FALSE flag of "X" being present:

dat[, numSpecial := sum(special == "X") * (special == "X"), by=order]
dat

#   rowid order line special numSpecial
#1:     1     A    1       X          1
#2:     2     B    1                  0
#3:     3     B    2       X          2
#4:     4     B    3       X          2
#5:     5     C    1       X          1
#6:     6     C    2                  0

You could also do it a bit differently like:

dat[, numSpecial := 0L][special == "X", numSpecial := .N, by=order]

Where dat was:

library(data.table)
dat <- structure(list(rowid = 1:6, order = c("A", "B", "B", "B", "C", 
"C"), line = c(1L, 1L, 2L, 3L, 1L, 2L), special = c("X", "", 
"X", "X", "X", "")), .Names = c("rowid", "order", "line", "special"
), row.names = c(NA, -6L), class = "data.frame")
setDT(dat)

Answer 2

You could use ave with a dummy variable (just filled with 1 s):

df$numSpecial <- ifelse(df$special == "X", ave(rep(1,nrow(df)), df$order, df$special, FUN = length), 0)

 df
#  rowid order line special numSpecial
#1     1     A    1       X          1
#2     2     B    1                  0
#3     3     B    2       X          2
#4     4     B    3       X          2
#5     5     C    1       X          1
#6     6     C    2                  0

Note I read in your data without the numSpecial column.

Answer 3

Using the dplyr package:

library(dplyr)

df %>% group_by(order) %>% 
  mutate(numSpecial = ifelse(special=="X", sum(special=="X"), 0))

  rowid order special numSpecial 1 1 AX 1 2 2 B 0 3 3 BX 2 4 4 BX 2 5 5 CX 1 6 6 C 0 

Answer 4

One other option using base R only would be to use aggregate:

# Your data
df <- data.frame(rowid = 1:6, order = c("A", "B", "B", "B", "C", "C"), special = c("X", "", "X", "X", "X", ""))

# Make the counts    
dat <- with(df,aggregate(x=list(answer=special),by=list(order=order,special=special),FUN=function(x) sum(x=="X")))

# Merge back to original dataset:
dat.fin <- merge(df,dat,by=c('order','special'))