coalesce with wrapr

November 3, 2018

(This article was first published on R – Win-Vector Blog, and kindly contributed to R-bloggers)

coalesce is a classic useful SQL operator that picks the first non-NULL value in a sequence of values.

We thought we would share a nice version of it for picking non-NA R with convenient operator infix notation wrapr::coalesce(). Here is a short example of it in action:


NA %?% 0

# [1] 0

A more substantial application is the following.


d <- wrapr::build_frame(
  "more_precise_sensor", "cheaper_back_up_sensor" |
  0.31                 , 0.25                     |
  0.41                 , 0.5                      |
  NA_real_             , 0.5                      )


#   more_precise_sensor cheaper_back_up_sensor
# 1                0.31                   0.25
# 2                0.41                   0.50
# 3                  NA                   0.50

d$measurement <- 
   d$more_precise_sensor %?% d$cheaper_back_up_sensor


#   more_precise_sensor cheaper_back_up_sensor measurement
# 1                0.31                   0.25        0.31
# 2                0.41                   0.50        0.41
# 3                  NA                   0.50        0.50

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