CODEWITHSUNDEEP
r
user3044487
user3044487

Reputation: 129

How to tell when data "change" in R?

with a dataset, one column is "1, 1, 1, ... 2, 2, 2, .. 3, 3, 3, 3 ..." with varying amounts of the same number repeated. I want to find the total of all the 1s, all the 2s and so forth... How can I do that with a for loop? How can I tell when the number in that column changes?

This is what I'm thinking: 

for (i in 1: length(data)) {
for (j in [beginning of first] to [end of first]) {
   #do something
}
}

But how do I find the beginning of first and end of first? Thank you

Upvotes: 0

Views: 47

Answers (1)

nico
nico

Reputation: 51640

As a note of general advice, if you are using R and start thinking of using a for loop, you should see whether there is a better way to do that.

For instance, to solve your problem you just need to do:

table(data$columnName)

So, for instance

> set.seed(12345) # set seed, for reproducibility
> myvar <- rep(1:10, sample(1:20,10,rep=T)) # Generate some data
> myvar
  [1]  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  2  2  2  2  2  2  2  2  2  2
 [26]  2  2  2  2  2  2  2  2  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  3  4
 [51]  4  4  4  4  4  4  4  4  4  4  4  4  4  4  4  4  4  5  5  5  5  5  5  5  5
 [76]  5  5  6  6  6  6  7  7  7  7  7  7  7  8  8  8  8  8  8  8  8  8  8  8  9
[101]  9  9  9  9  9  9  9  9  9  9  9  9  9  9 10 10 10 10 10 10 10 10 10 10 10
[126] 10 10 10 10 10 10 10 10 10
> table(myvar)
myvar
 1  2  3  4  5  6  7  8  9 10 
15 18 16 18 10  4  7 11 15 20

Upvotes: 1

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