How can I make conditional selections using dplyr in R? - r

Question

I have the following situation. Given the table
df <- data.frame(ID = c(1, 2, 2, 3, 3, 4),
type = c("MC", "MC", "MK", "MC", "MK", "MC"),
value1 = c(512, 261, 4523, 1004, 1221, 2556),
value2 = c(726, 4000, 280, 998, 113, 6789))
I am trying to find a way to implement the following logic: If for an ID, both types (MC and MK) occur, use value1 from MK and value2 from MC. Otherwise (only the type MC occurs), use MC.
Hence, the final result is supposed to be:
data.frame(ID = c(1, 2, 3, 4),
type = c("MC", "MC", "MC", "MC"),
value1 = c(512, 4523, 1221, 2556),
value2 = c(726, 4000, 998, 6789))
Assuming the type MK is dropped after extracting the value1.

Answer 1

Another version with dplyr
library(dplyr)
df %>%
group_by(ID) %>%
mutate(value1 = ifelse(any(type == "MK"), value1[type=="MK"],value1[type=="MC"]),
value2 = value2[type == "MC"]) %>%
filter(type == "MC")
# ID type value1 value2
# <dbl> <fct> <dbl> <dbl>
#1 1 MC 512 726
#2 2 MC 4523 4000
#3 3 MC 1221 998
#4 4 MC 2556 6789
Here, for value1 we check value in "MK" if it is present or take corresponding "MC" value instead and for value2 by default we take "MC" value and keep only rows with type "MC". This is assuming every group (ID) would have a "MC" type row.

Answer 2

For efficiency I would definitely prefer #Andre Elrico' answer but here is a dplyr option. Try:
df <- data.frame(ID = c(1, 2, 2, 3, 3, 4),
type = c("MC", "MC", "MK", "MC", "MK", "MC"),
value1 = c(512, 261, 4523, 1004, 1221, 2556),
value2 = c(726, 4000, 280, 998, 113, 6789))
library(dplyr)
df %>%
reshape(., idvar = "ID", timevar = "type", direction = "wide") %>%
group_by(ID) %>%
mutate(value1 = ifelse(is.na(value1.MK), value1.MC, value1.MK),
value2 = ifelse(is.na(value2.MC), value2.MK, value2.MC),
type = "MC") %>%
select(ID, type, value1, value2)
# output
# A tibble: 4 x 4
# Groups: ID [4]
ID type value1 value2
<dbl> <chr> <dbl> <dbl>
1 1 MC 512 726
2 2 MC 4523 4000
3 3 MC 1221 998
4 4 MC 2556 6789

Answer 3

data.table solution
setDT(df1)[,{x=.SD;if(all(c("MC","MK") %in% type)){x$value1[] = last(value1)};first(x)},by=ID]
result:
# ID type value1 value2
#1 1 MC 512 726
#2 2 MC 4523 4000
#3 3 MC 1221 998
#4 4 MC 2556 6789
dplyr:
df1 %>% group_by(ID) %>% do(.,(function(x){if(all(c("MC","MK") %in% x$type)){x$value1[] = x$value1[x$type=="MK"]};x[1,]})(.))
# A tibble: 4 x 4
# Groups: ID [4]
# ID type value1 value2
# <dbl> <fct> <dbl> <dbl>
#1 1 MC 512 726
#2 2 MC 4523 4000
#3 3 MC 1221 998
#4 4 MC 2556 6789