Select random subset of Breeding Bird Survey (BBS) routes

This function randomly samples routes from within a stage.

sample_BBS_routes(dat = BBS_PA, years = c(1990, 2000, 2005),
  aou.code = 7610, max.sample = 50)

Arguments

dat	Dataframe containing BBS data. Must contain columns for Year, Aou species code and Route
years	Years for for which you want to generate data for
aou.code	American Ornithological Union (AOU) numeric species code
max.sample	Maximum number routes per year.

Examples

## Setting up dataframe to examine change over time
## Focal species: European starling (Aou code = 4940)
### Start with the raw BBS_PA dataframe
### The function sample_BBS_routes()
### randomly samples routes for years your specify.
### It selects routes from the entire state.
### Note: sample_BBS_routes() requires the Hmisc package to work

## Subset European starling data
### See help file for AOU_species_codes for further details
### on subsetting data based on a species numeric code
# NOT RUN {
BBS_PA_EUST <- BBS_PA %>% filter(Aou == 4940)

## select the years 1990, 2000, and 2010
BBS_PA_EUST_2 <-  sample_BBS_routes(dat = BBS_PA_EUST,
                                    years = c(1990,2000,2010),
                                    aou.code = 4940)

## Look at data subset that has been created
head(BBS_PA_EUST_2)
summary(BBS_PA_EUST_2)

##Plot the results with a boxplot
ggboxplot(data = BBS_PA_EUST_2,
     y = "SpeciesTotal",
   x = "Year")

## Save output
### data can be saved with write.csv(), eg:
write.csv(BBS_PA_EUST_2, file = "starling_change_over_time.csv")
# }