Where is `ecdf` saving its object? (and how to measure it?)

Question

I can't seem to understand where R saves the data for `ecdf`. Here is some code to illustrate this: ``` > set.seed(2016-10-30) > x <- rnorm(1e4) > y <- ecdf(x) > object.size(x) 80040 bytes > object.size(y) 3896 bytes > rm(x) > gc() used (Mb) gc trigger (Mb) max used (Mb) Ncells 602079 32.2 1168576 62.5 750400 40.1 Vcells 1183188 9.1 299644732 2286.2 750532746 5726.2 > object.size(y) 3896 bytes > plot(y) # still works... > ``` If the size of y is small, it means the data is saved somewhere. It is obviously not saved in x (as I removed it). - It is probably in some environment, but how would we access it? So where is this data saved, and how can it be accessed? - How would this effect memory.limit() ? (i.e.: caching or memory limits of running R processes)

Accepted Answer

There is a fantastic explanation of function closures, the enclosing, executing and calling environments in @hadley's Advanced R.

For your specific example, as noted in the comments, the size of the object, together with its enclosing environment is much larger:

```
pryr::compare_size(y)
```

You can see the objects that this entails, and their relative sizes using this:

```
sapply(codetools::findGlobals(y), function(x) object.size(get(x, environment(y))))
```

You can sum the last vector to see that this is indeed what `pryr::object_size` is reporting (164 kB on my machine).

Where is `ecdf` saving its object? (and how to measure it?)

Solution

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