randomizing data by category in R - r

Question

So I am a bit new with R, so forgive me if this is a silly question. I have a data set of behaviors that looks something like this:
time behavior
10:04:36 FEED
10:04:37 FEED
10:04:38 REST
10:04:39 REST
10:04:40 RUN
etc..
I have added a column that numbers each new behavior as a unique number, something like:
time behavior Number
10:04:36 FEED 1
10:04:37 FEED 1
10:04:38 REST 2
10:04:39 REST 2
10:04:40 RUN 3
Therefore, if the behaviors at 10:04:36 and 10:30:00 are both FEED, they are still recognized as different behavior events because they have different numbers. I then subsetted my data by behavior category so that I have a dataset of all one behavior. However, in this data set I have Number categories for each time I have a new behavior event, for example:
time behavior Number
10:04:36 FEED 1
10:04:37 FEED 1
10:30:00 FEED 10
10:30:01 FEED 10
10:30:02 FEED 10
11:01:00 FEED 21
11:01:01 FEED 21
etc...
Now, what I would like to do is randomize this new dataset by Number category. So I would like to tell R to take each chunk of data with the same Number value and reorganize these chunks. I tried to use sample(), but that only seems to work for randomizing by row. As you can see the Number categories are not all the same size either. Basically I would like to create a new matrix that looks something like this:
time behavior Number
10:30:00 FEED 10
10:30:01 FEED 10
10:30:02 FEED 10
11:01:00 FEED 21
11:01:01 FEED 21
10:04:36 FEED 1
10:04:37 FEED 1
So, I would like R to recognize each new Number category as a distinct event, and randomly reorganize the data by each new event, not by row.
Does anyone know a way to do what I am trying to do in R?

Answer 1

You could create a helper funciton, such as
reorderingFunc <- function(data, indxCol){
indx <- sample(unique(data[, indxCol]))
data[order(unique(data[, indxCol])[match(data[, indxCol], indx)]), ]
}
Testing
set.seed(111) # Setting a seed so the outcome of `sample` be reproducible
reorderingFunc(df, "Number")
# time behavior Number
# 3 10:30:00 FEED 10
# 4 10:30:01 FEED 10
# 5 10:30:02 FEED 10
# 6 11:01:00 FEED 21
# 7 11:01:01 FEED 21
# 1 10:04:36 FEED 1
# 2 10:04:37 FEED 1