How to split data into training/testing sets using sample function

Question

How to split data into training/testing sets using sample function

I've quite recently started utilizing R and I don't know how to incorporate my dataset with the following example code:

sample(x, size, replace = FALSE, prob = NULL)

I have a dataset that I need to place into a training (75%) and testing (25%) set. I don't know what information I should place into the x and size? Is x the dataset file, and size what number of samples I have?

sample split r-language

4 years ago by vishaljlf39

3 Answers

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**espadacoder11** · Answer 1 · 2021-07-07T13:10:05

There are numerous approaches to achieve data partitioning. For a more complete approach take a look at the createDataPartition function in the caTools package.

Here is a simple example:



data(mtcars)



## 75% of the sample size

smp_size <- floor(0.75 * nrow(mtcars))



## set the seed to make your partition reproducible

set.seed(123)

train_ind <- sample(seq_len(nrow(mtcars)), size = smp_size)



train <- mtcars[train_ind, ]

test <- mtcars[-train_ind, ]

**sandhya6gczb** · Answer 2 · 2021-07-08T14:21:26

I would use dplyr for this, makes it super simple. It does require an id variable in your data set, which is a good idea anyway, not only for creating sets but also for traceability during your project. Add it if doesn't contain already.



mtcars$id <- 1:nrow(mtcars)

train <- mtcars %>% dplyr::sample_frac(.75)

test  <- dplyr::anti_join(mtcars, train, by = 'id')

**pankajshivnani123** · Answer 3 · 2021-07-12T11:55:38

It can be easily done by:



set.seed(101) # Set Seed so that same sample can be reproduced in future also

# Now Selecting 75% of data as sample from total 'n' rows of the data  

sample <- sample.int(n = nrow(data), size = floor(.75*nrow(data)), replace = F)

train <- data[sample, ]

test  <- data[-sample, ]

By using caTools package:

require(caTools)

set.seed(101) 

sample = sample.split(data$anycolumn, SplitRatio = .75)

train = subset(data, sample == TRUE)

test  = subset(data, sample == FALSE)

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How to split data into training/testing sets using sample function

3 Answers

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