context("Sample")
# Basic behaviour -------------------------------------------------------------
test_that("sample preserves class", {
expect_is(sample_n(mtcars, 1), "data.frame")
expect_is(sample_n(tbl_df(mtcars), 1), "tbl_df")
expect_is(sample_frac(mtcars, 1), "data.frame")
expect_is(sample_frac(tbl_df(mtcars), 1), "tbl_df")
})
# Ungrouped --------------------------------------------------------------------
df <- data.frame(
x = 1:2,
y = c(0, 1)
)
test_that("sample respects weight", {
# error message from base R
expect_error(sample_n(df, 2, weight = y))
expect_equal(sample_n(df, 1, weight = y)$x, 2)
expect_error(
sample_frac(df, 2),
"`size` of sampled fraction must be less or equal to one, set `replace` = TRUE to use sampling with replacement",
fixed = TRUE
)
expect_error(
sample_frac(df %>% group_by(y), 2),
"`size` of sampled fraction must be less or equal to one, set `replace` = TRUE to use sampling with replacement",
fixed = TRUE
)
# error message from base R
expect_error(sample_frac(df, 1, weight = y))
expect_equal(sample_frac(df, 0.5, weight = y)$x, 2)
})
test_that("sample_* error message", {
expect_error(
check_weight(letters[1:2], 2),
"`weight` must be a numeric, not character",
fixed = TRUE
)
expect_error(
check_weight(-1:-2, 2),
"`weight` must be a vector with all values nonnegative, not -1",
fixed = TRUE
)
expect_error(
check_weight(letters, 2),
"`weight` must be a numeric, not character"
)
})
test_that("sample gives informative error for unknown type", {
expect_error(
sample_n(list()),
"`tbl` must be a data frame, not list",
fixed = TRUE
)
expect_error(
sample_frac(list()),
"`tbl` must be a data frame, not list",
fixed = TRUE
)
})
# Grouped ----------------------------------------------------------------------
test_that("sampling grouped tbl samples each group", {
sampled <- mtcars %>% group_by(cyl) %>% sample_n(2)
expect_is(sampled, "grouped_df")
expect_groups(sampled, "cyl")
expect_equal(nrow(sampled), 6)
expect_equal(sampled$cyl, rep(c(4, 6, 8), each = 2))
})
test_that("can't sample more values than obs (without replacement)", {
by_cyl <- mtcars %>% group_by(cyl)
expect_error(
sample_n(by_cyl, 10),
"`size` must be less or equal than 7 (size of data), set `replace` = TRUE to use sampling with replacement",
fixed = TRUE
)
})
test_that("grouped sample respects weight", {
df2 <- tibble(
x = rep(1:2, 100),
y = rep(c(0, 1), 100),
g = rep(1:2, each = 100)
)
grp <- df2 %>% group_by(g)
# error message from base R
expect_error(sample_n(grp, nrow(df2) / 2, weight = y))
expect_equal(sample_n(grp, 1, weight = y)$x, c(2, 2))
# error message from base R
expect_error(sample_frac(grp, 1, weight = y))
expect_equal(sample_frac(grp, 0.5, weight = y)$x, rep(2, nrow(df2) / 2))
})
test_that("grouped sample accepts NULL weight from variable (for saeSim)", {
df <- tibble(
x = rep(1:2, 10),
y = rep(c(0, 1), 10),
g = rep(1:2, each = 10)
)
weight <- NULL
expect_error(sample_n(df, nrow(df), weight = weight), NA)
expect_error(sample_frac(df, weight = weight), NA)
grp <- df %>% group_by(g)
expect_error(sample_n(grp, nrow(df) / 2, weight = weight), NA)
expect_error(sample_frac(grp, weight = weight), NA)
})
test_that("sample_n and sample_frac can call n() (#3413)", {
df <- tibble(
x = rep(1:2, 10),
y = rep(c(0, 1), 10),
g = rep(1:2, each = 10)
)
gdf <- group_by(df, g)
expect_equal(sample_n(df, n()), df)
expect_equal(sample_n(gdf, n()), gdf)
expect_equal(nrow(sample_n(df, n()-2L)), nrow(df)-2)
expect_equal(nrow(sample_n(gdf, n()-2L)), nrow(df)-4)
})
test_that("sample_n and sample_frac handles lazy grouped data frames (#3380)", {
df1 <- data.frame(x = 1:10, y = rep(1:2, each=5))
df2 <- data.frame(x = 6:15, z = 1:10)
res <- df1 %>% group_by(y) %>% anti_join(df2, by="x") %>% sample_n(1)
expect_equal(nrow(res), 1L)
res <- df1 %>% group_by(y) %>% anti_join(df2, by="x") %>% sample_frac(0.2)
expect_equal(nrow(res), 1L)
})
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