How to do random sample from ff object

Question

I want to extract the number of 1000 values from large size of ff object in R.

I have tried sample_frac from dplyr package, but this results in error as below;

Error: tbl must be a data frame, not a ffdf object

How can I solve this problem?

Answer 1

You can use ffbase2 package. It adds the dplyr interface to ff object

install.packages("devtools")
devtools::install_github("edwindj/ffbase2")

And read ff object as tbl with tbl_ffdf function.

iris_f <- tbl_ffdf(iris)

species <- 
   iris_f %>%
   group_by(Species) %>%
   summarise(petal_width = sum(Petal.Width))