Inconsistent rounding Issue

Round results for rcaaqs::pm_24h_caaqs() is inconsistent depending on the range of data set. In the example below, if data provided is from 2011-2015, the metric_value for 2015 is 28, but when this same data is filtered to 2013-2015, the metric_value for 2015 is 29. Noted that the annual values for each remain the same.

`# -rounding check
library(dplyr)
library(lubridate)

# -create pseudo data
data <- tibble(
year = c(2011,2012,2013,2014,2015),
value=c(27.8,27.9,32.6,28.5,24.4)
)
start_date <- ymd_hm('2011-01-01 00:00')
end_date <- ymd_hm('2015-12-31 23:00')

dates <- seq(from = start_date,to = end_date, by='hour')
df <- tibble(
date_time=dates
) %>%
cross_join(tibble(site = 'site1')) %>%
mutate(year = year(date_time)) %>%
left_join(data)

df1 <- df
df2 <- df %>%
filter(year>=2013)

test1 <- rcaaqs::pm_24h_caaqs(data = df1)
test2 <- rcaaqs::pm_24h_caaqs(data = df2)
test1$caaqs
test2$caaqs`

test1$caaqs
# A tibble: 5 × 10
caaqs_year min_year max_year n_years metric metric_value caaqs flag_daily_incomplete flag_yearly_incomplete flag_two_of_three_years

1 2011 2011 2011 1 pm2.5_24h NA Insufficient Data NA FALSE FALSE
2 2012 2011 2012 2 pm2.5_24h 28 Not Achieved NA FALSE TRUE
3 2013 2011 2013 3 pm2.5_24h 29 Not Achieved NA FALSE FALSE
4 2014 2012 2014 3 pm2.5_24h 30 Not Achieved NA FALSE FALSE
5 2015 2013 2015 3 pm2.5_24h 28 Not Achieved NA FALSE FALSE
> test2$caaqs
# A tibble: 3 × 10
caaqs_year min_year max_year n_years metric metric_value caaqs flag_daily_incomplete flag_yearly_incomplete flag_two_of_three_years

1 2013 2013 2013 1 pm2.5_24h NA Insufficient Data NA FALSE FALSE
2 2014 2013 2014 2 pm2.5_24h 31 Not Achieved NA FALSE TRUE
3 2015 2013 2015 3 pm2.5_24h 29 Not Achieved NA FALSE FALSE

Start by running the supplied R example and inspect the implementation of rcaaqs::pm_24h_caaqs(). Compare how the 2011–2015 and 2013–2015 inputs produce their 2015 metric_value, then verify that the result is consistent without changing the annual values.

Written by the indexing model from the issue text.