tidyverse: grouped summaries (with summerize)

That's what I thought I did. I'll rewrite the script and work toward the
output I need.

Still not the correct syntax. Command is now:
disc_by_month %>%
     group_by(year, month) %>%
     summarize(disc_by_month, vol = mean(cfs, na.rm = TRUE))

and results are:

source('disc.R')

`summarise()` has grouped output by 'year', 'month'. You can override using the `.groups` argument.

disc_by_month

# A tibble: 590,940 ? 6
# Groups:   year, month [66]
     year month   day  hour   min    cfs
    <int> <int> <int> <int> <int>  <dbl>
  1  2016     3     3    12     0 149000
  2  2016     3     3    12    10 150000
  3  2016     3     3    12    20 151000
  4  2016     3     3    12    30 156000
  5  2016     3     3    12    40 154000
  6  2016     3     3    12    50 150000
  7  2016     3     3    13     0 153000
  8  2016     3     3    13    10 156000
  9  2016     3     3    13    20 154000
10  2016     3     3    13    30 155000
# ? with 590,930 more rows

The grouping is still not right. I expected to see a mean value for each
month of each year in the data set, not for each minute.

Rich