# A simple use case with vectors of input
single_value(c(NA, 1))
# Multiple, different values of missing can be given
single_value(c(NA, "a"), missing = c(NA, "a"))
# A typical use case with a grouped data.frame used for input and the output
# (`B` is guaranteed to have a single value and only one row, in this case)
data.frame(A = rep(1:3, each = 2),
B = c(rep(4:6, each = 2))) %>%
dplyr::group_by(A) %>%
dplyr::summarize(
B = single_value(B)
)
try(
# info is useful to give when multiple values may be found to see what
# grouping variable or what calculation is causing the error
data.frame(A = rep(1:3, each = 2),
B = c(rep(1:2, each = 2), 1:2)) %>%
dplyr::group_by(A) %>%
dplyr::mutate(
C = single_value(B, info = paste("Calculating C for group A=", A))
)
)
Run the code above in your browser using DataLab