Debugger: indexing

Instructions

Bugs are an ever-present challenge in programming. With their red text and baffling messages, errors are among the most intimidating parts of learning to code. Perhaps even more frustrating are silent bugs - the code runs but the results just aren’t right.

Debugger exercises will present you with buggy code - either an error or incorrect result. Your task will be to describe the intent of the code, diagnose the error, and use your problem solving skills to find a solution. With practice, these exercises will demystify errors and you’ll gain confidence in your coding abilities.

Begin by creating a new script in your eds221/day2 folder called day2pm-debugger.R.

For each of the following code chunks

  1. Explain in plain language what the code chunk is supposed to do.
  2. Copy-paste the chunk into your script and run it to see the bug.
  3. Describe the bug. Is it an error? An incorrect value? What did you expect, versus what did you find?
  4. Fix the bug. Verify the code runs as expected.

Bugs

Bug 1

“Brianna said the coral cover pre-2020 never dropped below 10% - can you double check that?”

survey_years <- seq(2008, 2024, by = 2)
coral_cover_pct <- c(34.53, 22.26, 11.66, 9.25, 14.05, 22.30, 30.35, 16.35, 5.74)

pre_2020_coral <- survey_years[coral_cover_pct < 2020]
min(pre_2020_coral)

Bug 2

“Did you get the sea level model predictions for the Coastal Commission meeting?”

sea_level_2100_ft <- c(1.7, 2.0, 2.6, 10)
names(sea_level_2100_ft) <- c("RCP 2.6", "RCP 4.5", "RCP 8.5", "H++")
worst_case_rcp <- "RCP 8.5"
sea_level_2100_ft["worst_case_rcp"]

Bug 3

“Hey Randall, it looks like you recorded a finch as a towhee. Can you fix that?”

songbird_survey <- data.frame(
  species = c("California Towhee", "House Finch", "House Sparrow"),
  count = c(9L, 6L, 8L),
  song_freq_khz = c(4.99, 2.66, 4.08),
  is_native = c(TRUE, TRUE, FALSE)
)

wrong_count_towhee <- songbird_survey$count[species == "California Towhee"]
wrong_count_finch <- songbird_survey$count[species == "House Finch"]
right_count_towhee <- wrong_count_towhee - 1
right_count_finch <- wrong_count_finch + 1

songbird_survey$count[species == "California Towhee"] <- right_count_towhee
songbird_survey$count[species == "House Finch"] <- right_count_finch
songbird_survey