Allow parameter inequalities in R syntax in addition to API syntax

[potterzot]

The API uses:

• __LE = <=
• __LT = <
• __GT = >
• __GE = >=
• __LIKE = like
• __NOT_LIKE = not like
• __NE = not equal

appended to the parameter name to allow for inequalities. It would be nice is users could specify year >= 2012 and have that be translated into year__GE = 2012 in the query.

[rdinter]

For the conditional year values, I'd suggest looking at lines 85-114 of utils in usdarnass (https://github.com/rdinter/usdarnass/blob/master/R/utils.R):

# Conditional year values
conditional_years <- function(x) {
  # Check to see if year used a logical operator
  years <- trimws(x)
  punct <- grepl("[[:punct:]]", years)
  punct_years <- as.numeric(gsub("[[:punct:]]", "", years))
  
  # Conditional year values
  # __LE = <= 
  # __LT = < 
  # __GT = > 
  # __GE = >= 
  # __LIKE = like 
  # __NOT_LIKE = not like 
  # __NE = not equal 
  year     <- punct_years[!punct]
  year__LE <- punct_years[(grepl("^=<|^<=", years) | grepl("=>$|>=$", years))]
  year__LT <- punct_years[((grepl("^<", years) | grepl(">$", years)) &
                             !grepl("=", years))]
  year__GE <- punct_years[(grepl("^=>|^>=", years) | grepl("=<$|<=$", years))]
  year__GT <- punct_years[((grepl("^>", years) | grepl("<$", years)) &
                             !grepl("=", years))]
  
  results <- list(year = year,
                  year__LE = year__LE,
                  year__LT = year__LT,
                  year__GE = year__GE,
                  year__GT = year__GT)
  return(results)
}

Basically treat the argument for year as a character and search through for punctuation that might be at the beginning or end.

One issue is that the API is finicky if you want to use multiple conditionals to create a range of year values. The API seems to only take the first conditional related to year as the subset rdinter/usdarnass#3

[potterzot]

@rdinter thanks for this as well! Hopefully I'll get to tackle this sometime soon.