For loops in R for data compilation

Question

I have a data frame that has a column populated with 0s and 1s. Here is an example of what that data looks like:

0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 1 0 0 0 0  ... etc.

I need to format the data so that it counts the number of consecutive 0s and 1s, like this:

I'm new to R and am not sure how to do this, but here's how I would do it in JavaScript. I would love some guidance on how to replicate this result in R. Thank you in advance for your help!

var data = [0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 1, 0, 0, 0];
var result = [];

for (var i = 0; i < data.length; i++) {
  var item = {};
  item[data[i]] = 1;
  if (!result.length) {
    result.push(item);
  } else {
    var lastItem = result[result.length - 1];
    if (lastItem[data[i]]) {
      lastItem[data[i]] += 1;
    } else {
      result.push(item);
    }
  }
}

console.log(result)

@PierreLafortune Haha, thanks, I'm new to JavaScript too, so that might not have been the most efficient way to do it! How would I convert this to a table/dataframe/matrix? I tried matrix(unlist ( rle(data) ), ncol = 2, byrow = TRUE) but that's not quite right. — Aakriti, Oct 26 '16 at 19:38
* I want to convert it for easier viewing because I have over a million observations. — Aakriti, Oct 26 '16 at 19:40

Pierre L · Accepted Answer · 2016-10-26T19:45:06.127

1

There is a function for that. rle calculates the run-length of each element in the vector. There are two parts to the output, the lengths of the runs, and the values themselves:

rle(x)
#Run Length Encoding
#  lengths: int [1:7] 5 4 10 3 1 2 4
#  values : int [1:7] 0 1 0 1 0 1 0

To create a matrix, we can use:

with(rle(x), cbind(values, lengths))

edited Oct 26 '16 at 19:45

answered Oct 26 '16 at 19:35

Pierre L

28,203
6
47
69

For loops in R for data compilation

1 Answers1