Implementing PubChem PUG-View web service

[stitam]

The Pubchem PUG-View web service allows the programmer to access information from the PubChem content pages (e.g. https://pubchem.ncbi.nlm.nih.gov/compound/176). The proposed function which implements this functionality is pc_sect() as it accesses a section of the content pages (I struggled with naming this function so I am open to suggestions). An example:

pc_sect(c(176, 311), "pka")

This returns a tibble of pKa a values. Under the hood the function uses pc_page() to retrieve a list of content pages and pc_extract() to extract information from these content pages and assemble the tibble.

Some issues I feel we should discuss:

• pc_page() uses webchem_submit() (now renamed to submit_request()) to submit POST requests in a standardised manner. This function is an attempt to standardise all http requests in webchem. Do you think this function would help? Edit: removed the function, let's discuss this as a separate issue.
• pc_page() and pc_extract() use the data.tree package, which is a new dependency. It would be great not to depend on another package, but I couldn't navigate the content pages otherwise. Can you suggest an alternative?

PR task list:

• Update NEWS
• Add tests (if appropriate)
• Update documentation with devtools::document()
• Check package passed

[Aariq]

This function works exactly how I'd expect it to from your description. I think it's a great addition to the package. I have a few documentation requests and some other code suggestions that you can take or leave.

[stitam]

I updated the PR based on @Aariq's comments. The package is still not building, I think this has to do with AppVeyor being unable to check the examples because some of the webservices are down.