Export cross-validation blocks/folds

[HendrikHamacher]

Hi,

it's not an issue per se, but I was wondering if it's possible to export the output from cv_spatial (such as the table with the different points for each fold + coordinates) to a csv file? I tried to do it, but R states that it cannot convert class "cv_spatial" into a datafrme.

I am relatively new to R, however I managed to create the blocks and different points per fold. I would like to use this for a classification in Google Earth Engine.

Best regards,
Hendrik

[rvalavi]

Hi @HendrikHamacher

This is pretty easy, You just need to add the folds_ids to your points and export it as a csv.

This example is from the cv_spatial help file:

library(blockCV)
library(sf)

# import presence-absence species data
points <- read.csv(system.file("extdata/", "species.csv", package = "blockCV"))
# make an sf object from data.frame
pa_data <- sf::st_as_sf(points, coords = c("x", "y"), crs = 7845)

# hexagonal spatial blocking by specified size and random assignment
sb1 <- cv_spatial(x = pa_data,
                  column = "occ",
                  size = 450000,
                  k = 5,
                  selection = "random",
                  iteration = 50)

# check to see the number of folds equal your data points (this must be TRUE)
length(sb1$folds_ids) == nrow(points)

# add the fold IDs to the original dataframe
points$folds <- sb1$folds_ids
head(points)

# export points dataframe as a CSV file
write.csv(points, "points_with_cvfolds.csv")

[HendrikHamacher]

Hi @rvalavi

thanks for clarifying with the example, that really helped!