[help] Loading stantargets objects from outside the targets workflow

[bmaitner]

Help

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Description

Is it possible to load a stantargets object from outside of a targets directory? For example, with other targets files in the _targets/objects folder , I can load these using readRDS(). However, whenever I try this with files generated by stantargets (e.g., summary or draws objects), I receive an error stating "unknown input format".

# Make a temp directory
  temp <- tempdir()

# Link to a targets object created by targets  
  stantargets_object <- "https://github.com/AdamWilsonLab/emma_model/raw/targets-runs/_targets/objects/model_output_data_e4183434"
  
# Link to a targets object created by stantargets  
targets_object <- "https://github.com/AdamWilsonLab/emma_model/raw/targets-runs/_targets/objects/dyndata_training"

# Download files to temp dir
  download.file(url = stantargets_object,
                destfile = file.path(temp,basename(stantargets_object)))
  
  download.file(url = targets_object,
                destfile = file.path(temp,basename(targets_object)))

# Attempt to load files:  
  readRDS(file.path(temp, basename(stantargets_object))) #"Unknown input format"
#> Error in readRDS(file.path(temp, basename(stantargets_object))): unknown input format

  readRDS(file.path(temp, basename(targets_object)))|>
    head() # Works fine
#>    cellID       date most_recent_burn_date ndvi time_since_fire age
#> 1 2895983 2000-12-01                     0   NA              NA  NA
#> 2 2895985 2000-12-01                     0   NA              NA  NA
#> 3 2895986 2000-12-01                     0   NA              NA  NA
#> 4 2898019 2000-12-01                     0   NA              NA  NA
#> 5 2898020 2000-12-01                     0   NA              NA  NA
#> 6 2900051 2000-12-01                     0   NA              NA  NA

^{Created on 2023-07-21 with reprex v2.0.2}

[wlandau]

My recommendation at ropensci/targets#1097 (reply in thread) would help if the files are local, but it looks like you are loading it from a GitHub repo. Also, stantargets uses format = "qs" and format = "fst", so you might need qs::qread() and/or fst::read_fst() for the code in your comment to work.

If you want to store the data remotely and access it locally, you could use built-in cloud storage: https://books.ropensci.org/targets/data.html#cloud-storage

[bmaitner]

Ahh, I see. I was under the impression that everything without an extension in the _targets/objects folder was an RDS file (per https://books.ropensci.org/targets-design/data.html#targets ). Now that I know it contains the other types, I can put together a little helper function to load objects of unknown type. Thanks so much for the quick reply and the awesome tools! :)