R:Count the daily number of a variable distinguish per ID

Question

Here is my data:

ID        Date             v
ID1         1              v1
ID1         1              v1
ID1         1              v8
ID1         2              v5
ID1         2              v3
ID1         3              v3
ID2         1              v7
ID2         2              v15
ID2         2              v15
ID2         3              v3

I want to calculate the number of v distinguish per day and per ID. As my data above, I wanna get the result like:

ID        Date             v         daily_v_distinguish_ID
ID1         1              v1            2
ID1         1              v1            NA
ID1         1              v8            NA
ID1         2              v5            2
ID1         2              v3            NA
ID1         3              v3            1
ID2         1              v7            1
ID2         2              v15           1
ID2         2              v15           NA
ID2         3              v3            1

How to solve that? Thanks you in advance!

And Then, if I only want to calculate the daily number of v (NOT distingunish) per ID, how to change the code?

The expected result:

ID        Date             v         daily_v_distinguish_ID    daily_v_ID
ID1         1              v1            2                       3
ID1         1              v1            NA                      3
ID1         1              v8            NA                      3
ID1         2              v5            2                       2
ID1         2              v3            NA                      2
ID1         3              v3            1                       1
ID2         1              v7            1                       1
ID2         2              v15           1                       2
ID2         2              v15           NA                      2
ID2         3              v3            1                       1

Answer 1

You can try using the devel version of data.table ie. v1.9.5. Instructions to install the devel version are here

library(data.table)#v1.9.5+
setDT(df1)[,  daily_v_ID:= ifelse((1:.N)==1L, uniqueN(v), NA) , by = .(ID, Date)]

Or

setDT(df1)[,  daily_v_ID := c(uniqueN(v), rep(NA, .N-1)), by = .(ID, Date)]

Or as suggested by @David Arenburg

indx <- setDT(df1)[, .(.I[1L], uniqueN(v)), by = .(ID, Date)] 
df1[indx$V1, daily_v_ID := indx$V2]

Or using dplyr

library(dplyr)
df1 %>% 
  group_by(ID,Date) %>%
  mutate(daily_v_ID= ifelse(row_number()==1, n_distinct(v), NA))

Or with base R

df1$daily_v_ID <- with(df1, ave(as.numeric(factor(v)), Date,ID,
      FUN= function(x) NA^(seq_along(x)!=1)*length(unique(x))))

Update

For the edited post, we create a variable ('daily_v_ID') by getting the length(v) or in the data.table, we can use .N

setDT(df1)[, c('daily_v_distinguish_ID', 'daily_v_ID'):= list( c(uniqueN(v),
                  rep(NA, .N-1)), .N), by = .(ID, Date)]
df1
#       ID Date   v daily_v_distinguish_ID daily_v_ID
#  1: ID1    1  v1                      2          3
#  2: ID1    1  v1                     NA          3
#  3: ID1    1  v8                     NA          3
#  4: ID1    2  v5                      2          2
#  5: ID1    2  v3                     NA          2
#  6: ID1    3  v3                      1          1
#  7: ID2    1  v7                      1          1
#  8: ID2    2 v15                      1          2
#  9: ID2    2 v15                     NA          2
# 10: ID2    3  v3                      1          1

NOTE: uniqueN is introduced in the v1.9.5. For earlier versions, we can use unique(length(v))

Or using dplyr

df1 %>% 
    group_by(ID, Date) %>%
    mutate(daily_v_distinguish_ID = ifelse(row_number()==1,
                                        n_distinct(v), NA), 
           daily_v_ID =n())