How to randomly split data into three equal sizes?

Question

I have a dataset with 9558 rows from three different projects. I want to randomly split this dataset in three equal groups and assign a unique ID for each group, so that Project1_Project_2_Project3 becomes Project1, Project2 and Project3.

I have tried many things, and googled codes from people with similar problem as I have. I have used sample_n() and sample_frac(), but unfortunately I can't solve this issue myself :/

I have made an example of my dataset looking like this:

ProjectName <- c("Project1_Project2_Project3")
data <- data.frame(replicate(10,sample(0:1,9558,rep=TRUE)))
data <- data.frame(ProjectName, data)

And the output should be randomly split in three equal group of nrow=3186 and then assigned to the values

ProjectName Count of rows
Project1     3186
Project2     3186
Project3     3186

Answer 1

IMO it should be sufficient to assign just random project names.

dat$ProjectName <- sample(factor(rep(1:3, length.out=nrow(dat)), 
                          labels=paste0("Project", 1:3)))

Result

head(dat)
#   X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 ProjectName
# 1  1  1  0  1  1  1  1  0  1   0    Project1
# 2  1  1  1  1  1  1  0  0  1   0    Project1
# 3  0  0  1  1  0  0  0  1  1   1    Project1
# 4  1  1  1  0  1  0  1  1  0   1    Project3
# 5  1  0  0  1  1  1  1  0  0   1    Project1
# 6  1  0  0  0  0  1  0  1  1   1    Project3

table(dat$ProjectName)
# Project1 Project2 Project3 
#     3186     3186     3186 

Data

set.seed(42)
dat <- data.frame(replicate(10, sample(0:1, 9558, rep=TRUE)))