Dear all, I'm having trouble with something which unfortunately I absolutely have 0 idea where to start. I have written a function called purely() which allows to catch any condition. A decorated function with purely() will return a list of two elements $result and $log. If everything goes well, $result holds the result, and if something happens, $result is NA and $log has the error/message/warning.
purely() works for any function I've tried, but not for group_by() nor count()(which I guess uses group_by() under the hood).
My guess is that group_by() is a very special function that does something unusual, which purely() doesn't know how to deal with. What's weird, is that no condition is raised, so $log is empty!
Any idea? Below a reprex.
purely <- function(.f){
function(..., .log = "Log start..."){
res <- rlang::try_fetch(
eval_tidy(.f(...)),
condition = function(cnd) cnd
)
final_result <- list(
result = NULL,
log = NULL
)
final_result$result <- if(c("condition") %in% class(res)){
NA
} else {
res
}
final_result$log <- if(c("condition") %in% class(res)){
res$message
} else {
NA
}
final_result
}
}
# on a simple function
purely(log)(10)
#> $result
#> [1] 2.302585
#>
#> $log
#> [1] NA
# error gets caught
purely(log)("10")
#> $result
#> [1] NA
#>
#> $log
#> [1] "non-numeric argument to mathematical function"
# these, and many others work
purely(dplyr::select)(mtcars, am, starts_with("c"))
#> $result
#> am cyl carb
#> Mazda RX4 1 6 4
#> Mazda RX4 Wag 1 6 4
#> Datsun 710 1 4 1
#> Hornet 4 Drive 0 6 1
#> Hornet Sportabout 0 8 2
#> Valiant 0 6 1
#> Duster 360 0 8 4
#> Merc 240D 0 4 2
#> Merc 230 0 4 2
#> Merc 280 0 6 4
#> Merc 280C 0 6 4
#> Merc 450SE 0 8 3
#> Merc 450SL 0 8 3
#> Merc 450SLC 0 8 3
#> Cadillac Fleetwood 0 8 4
#> Lincoln Continental 0 8 4
#> Chrysler Imperial 0 8 4
#> Fiat 128 1 4 1
#> Honda Civic 1 4 2
#> Toyota Corolla 1 4 1
#> Toyota Corona 0 4 1
#> Dodge Challenger 0 8 2
#> AMC Javelin 0 8 2
#> Camaro Z28 0 8 4
#> Pontiac Firebird 0 8 2
#> Fiat X1-9 1 4 1
#> Porsche 914-2 1 4 2
#> Lotus Europa 1 4 2
#> Ford Pantera L 1 8 4
#> Ferrari Dino 1 6 6
#> Maserati Bora 1 8 8
#> Volvo 142E 1 4 2
#>
#> $log
#> [1] NA
purely(dplyr::mutate)(mtcars, am2 = 2*am)
#> $result
#> mpg cyl disp hp drat wt qsec vs am gear carb am2
#> Mazda RX4 21.0 6 160.0 110 3.90 2.620 16.46 0 1 4 4 2
#> Mazda RX4 Wag 21.0 6 160.0 110 3.90 2.875 17.02 0 1 4 4 2
#> Datsun 710 22.8 4 108.0 93 3.85 2.320 18.61 1 1 4 1 2
#> Hornet 4 Drive 21.4 6 258.0 110 3.08 3.215 19.44 1 0 3 1 0
#> Hornet Sportabout 18.7 8 360.0 175 3.15 3.440 17.02 0 0 3 2 0
#> Valiant 18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1 0
#> Duster 360 14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4 0
#> Merc 240D 24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2 0
#> Merc 230 22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2 0
#> Merc 280 19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4 0
#> Merc 280C 17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4 0
#> Merc 450SE 16.4 8 275.8 180 3.07 4.070 17.40 0 0 3 3 0
#> Merc 450SL 17.3 8 275.8 180 3.07 3.730 17.60 0 0 3 3 0
#> Merc 450SLC 15.2 8 275.8 180 3.07 3.780 18.00 0 0 3 3 0
#> Cadillac Fleetwood 10.4 8 472.0 205 2.93 5.250 17.98 0 0 3 4 0
#> Lincoln Continental 10.4 8 460.0 215 3.00 5.424 17.82 0 0 3 4 0
#> Chrysler Imperial 14.7 8 440.0 230 3.23 5.345 17.42 0 0 3 4 0
#> Fiat 128 32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1 2
#> Honda Civic 30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2 2
#> Toyota Corolla 33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1 2
#> Toyota Corona 21.5 4 120.1 97 3.70 2.465 20.01 1 0 3 1 0
#> Dodge Challenger 15.5 8 318.0 150 2.76 3.520 16.87 0 0 3 2 0
#> AMC Javelin 15.2 8 304.0 150 3.15 3.435 17.30 0 0 3 2 0
#> Camaro Z28 13.3 8 350.0 245 3.73 3.840 15.41 0 0 3 4 0
#> Pontiac Firebird 19.2 8 400.0 175 3.08 3.845 17.05 0 0 3 2 0
#> Fiat X1-9 27.3 4 79.0 66 4.08 1.935 18.90 1 1 4 1 2
#> Porsche 914-2 26.0 4 120.3 91 4.43 2.140 16.70 0 1 5 2 2
#> Lotus Europa 30.4 4 95.1 113 3.77 1.513 16.90 1 1 5 2 2
#> Ford Pantera L 15.8 8 351.0 264 4.22 3.170 14.50 0 1 5 4 2
#> Ferrari Dino 19.7 6 145.0 175 3.62 2.770 15.50 0 1 5 6 2
#> Maserati Bora 15.0 8 301.0 335 3.54 3.570 14.60 0 1 5 8 2
#> Volvo 142E 21.4 4 121.0 109 4.11 2.780 18.60 1 1 4 2 2
#>
#> $log
#> [1] NA
# these don't
purely(dplyr::group_by)(mtcars, cyl)
#> $result
#> [1] NA
#>
#> $log
#> [1] ""
purely(dplyr::count)(mtcars, cyl)
#> $result
#> [1] NA
#>
#> $log
#> [1] ""
Created on 2022-03-12 by the reprex package (v2.0.1)