Finding dates majority of data fall into (median/ CI?) in R

Question

I have a dataset containing a column of dates (daily values summed by week) and a column of values representing bird mortality. I need to find out the dates the majority of mortality fall into. The values are not normally distributed with a major peak at the end of July due to increased surveying effort. Some weeks had zero observed mortalities.

Date Observed	Value
2022-05-08	4
2022-05-22	1
2022-05-29	5
2022-06-05	1
2022-06-12	10
2022-06-19	64
2022-06-26	4
2022-07-10	800
2022-07-17	300
2022-07-24	207
2022-07-31	3002
2022-08-07	2

I'm not new to R but I am evidently rusty on my statistical analysis. Could anyone point me in the right direction?

I have tried simple things: estimating median of Date Observed (using summary and summaryStats(DateObserved, quartiles=TRUE)[[7]] from EnvStats library. But after plotting the values over time, I do not think the resulting quartiles look right. Also, tried fitting a linear model.

Thank you sincerely in advance for any leads!

Answer 1

library(tidyverse)
df_1 <- read_tsv(file="DateObserved Value
2022-05-08  4
2022-05-22  1
2022-05-29  5
2022-06-05  1
2022-06-12  10
2022-06-19  64
2022-06-26  4
2022-07-10  800
2022-07-17  300
2022-07-24  207
2022-07-31  3002
2022-08-07  2") |> mutate(dt=as.numeric(DateObserved))

dt_seq <- seq(from=min(df_1$dt),
              to = max(df_1$dt))

dt_seq_pretty_indx <- seq(from=min(df_1$dt),
                          to = max(df_1$dt),
                          length.out=6)
dt_seq_pretty <- seq(from=min(df_1$DateObserved),
                     to = max(df_1$DateObserved),
                     length.out=6)


plot(df_1$dt,
     df_1$Value, xaxt = "n")
axis(side=1,
     at = dt_seq_pretty_indx,
     labels=dt_seq_pretty)



myloess <- loess(Value ~ dt,df_1,span = 0.4)

pred <- predict(myloess,newdata = data.frame(dt=dt_seq))

lines(x=dt_seq,
      y=pred)

library(Hmisc)
wq <- wtd.quantile(x=dt_seq,
             weights = pred,
             probs = c(.25,.75))

abline(v=wq[1],col="blue")
abline(v=wq[2],col="blue")
print(as.Date(wq,origin="1970-01-01"))