Example spread

spread.R

library(tidyverse)

# here is a table that spreads the way you'd want (with two rows):

tribble(
   ~a, ~b, ~c,
  "a", "x", 3,
  "a", "y", 2,
  "b", "x", 4,
  "b", "y", 7
) %>% spread(b,c)

#  # A tibble: 2 x 3
#    a         x     y
#    <chr> <dbl> <dbl>
#  1 a         3     2
#  2 b         4     7

# here is a table that doesn't spread the way I would want (it has four rows). 
# I happen to know that it's because the function doesn't know how to collapse 'd',
# but it often don't notice it happen often at the time:

tribble(
   ~a, ~b, ~c, ~d,
  "a", "x", 3, "r",
  "a", "y", 2, "s",
  "b", "x", 4, "t",
  "b", "y", 7, "u"
) %>% spread(b,c)

# # A tibble: 4 x 4
#    a     d         x     y
#    <chr> <chr> <dbl> <dbl>
#  1 a     r         3    NA
#  2 a     s        NA     2
#  3 b     t         4    NA
#  4 b     u        NA     7