CODEWITHSUNDEEP
r
D idsea J
D idsea J

Reputation: 113

Using sample on Iris in R

I'm super new to R and struggling with the following excercise:

"Choose a random species from Iris and pull without putting back 50 rows that are not that species".

Iris:

Sepal.Length Sepal.Width Petal.Length Petal.Width    Species
1            5.1         3.5          1.4         0.2     setosa
2            4.9         3.0          1.4         0.2     setosa
3            4.7         3.2          1.3         0.2     setosa
4            4.6         3.1          1.5         0.2     setosa
..
150          5.9         3.0          5.1         1.8  virginica

I've come up with this so far:

set.seed(1)
y <- sample(150, 1)
y
x <- iris[y,5]
x

Which results in:

> set.seed(1)
> y <- sample(150, 1)
> y
[1] 68
> x <- iris[y,5]
> x
[1] versicolor
Levels: setosa versicolor virginica

Now I know that I have to sample all of Iris and choose 50 that are not versicolor. How could I do that?

I've tried something like this:

z <- sample(iris, 50, replace = FALSE, iris.species != x)
z

If anyone could enlighten me on how to use the sample command I'd be thankful.

Thanks

Upvotes: 1

Views: 358

Answers (1)

Ronak Shah
Ronak Shah

Reputation: 389135

You need to choose a random Species, unique(iris$Species) gives unique values of Species and sample to get 1 random value.

select_species <- sample(unique(iris$Species), 1)

Use subset to drop that species from the dataset.

result <- subset(iris, Species != select_species)

To chose random 50 rows from result you may do

sample_50 <- result[sample(nrow(result), 50), ]

Or as @r2evans suggested -

sample_50 <- dplyr::slice_sample(result, n = 50)

Upvotes: 1

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