Check if prism files exist

Helper function to check if files already exist in the prism download directory. Determines if files have not been downloaded yet, i.e., returns TRUE if they do not exist.

Usage

prism_check(prismfiles, lgl = FALSE, pre81_months = NULL)

Arguments

prismfiles

a list of full prism file names ending in ".zip".

lgl

TRUE returns a logical vector indicating those not yet downloaded; FALSE returns the file names that are not yet downloaded.

pre81_months

Numeric vector of months that will be downloaded, if downloading data before 1981. This is so that the existence of the data can be correctly checked, as the file includes all monthly data for a given year.

Value

a character vector of file names that are not yet downloaded or a logical vector indication those not yet downloaded.