Spreading + removing irrelevant columns

[jackdolgin]

Such a big fan of tidyr! (I hope I'm doing this right, I've only posted to stackoverflow)

CO2low <- CO2 %>% filter(conc < 250)

spread(CO2low, conc, uptake) #attempt1

#    Plant        Type  Treatment   95  175
# 1    Qn1      Quebec nonchilled 16.0 30.4
# 2    Qn2      Quebec nonchilled 13.6 27.3
# 3    Qn3      Quebec nonchilled 16.2 32.4

CO2low$randoms <- runif(nrow(CO2low), min=0, max=1)
spread(CO2low, conc, uptake) #attempt2
#   Plant        Type  Treatment      randoms   95  175
# 1    Qn1      Quebec nonchilled 1.539457e-01 16.0   NA
# 2    Qn1      Quebec nonchilled 5.429544e-01   NA 30.4
# 3    Qn2      Quebec nonchilled 1.415618e-01 13.6   NA
# 4    Qn2      Quebec nonchilled 8.917103e-01   NA 27.3

I'd like my second spread attempt to result in the same output as the first spread attempt, and though I imagine I could use 'select(-randoms)', is there an argument in spread that would say something along the lines of, 'Remove any other columns whose values aren't identical between the rows we'd spread over'?

[hadley]

Thanks for filing this issue because I was thinking about it and you've saved me some typing 😄

[hadley]

library(tidyr)
library(dplyr, warn.conflicts = FALSE)

CO2low <- CO2 %>% filter(conc < 250)
CO2low$randoms <- runif(nrow(CO2low), min=0, max=1)

CO2low %>% 
  pivot_wide(keys = Plant:Treatment, names_from = conc, values_from = uptake)
#> # A tibble: 12 x 5
#>    Plant Type        Treatment   `95` `175`
#>    <ord> <fct>       <fct>      <dbl> <dbl>
#>  1 Qn1   Quebec      nonchilled  16    30.4
#>  2 Qn2   Quebec      nonchilled  13.6  27.3
#>  3 Qn3   Quebec      nonchilled  16.2  32.4
#>  4 Qc1   Quebec      chilled     14.2  24.1
#>  5 Qc2   Quebec      chilled      9.3  27.3
#>  6 Qc3   Quebec      chilled     15.1  21  
#>  7 Mn1   Mississippi nonchilled  10.6  19.2
#>  8 Mn2   Mississippi nonchilled  12    22  
#>  9 Mn3   Mississippi nonchilled  11.3  19.4
#> 10 Mc1   Mississippi chilled     10.5  14.9
#> 11 Mc2   Mississippi chilled      7.7  11.4
#> 12 Mc3   Mississippi chilled     10.6  18

^{Created on 2019-03-06 by the reprex package (v0.2.1.9000)}