Hello,
Clean R 3.6.1 session on Ubuntu 19.04, RStudio 1.1.453. sessionInfo() at
the end.
I can reproduce this.
counttt <- 0
`[[.MYCLASS` = function(x, ...) {
counttt <<- counttt + 1
# browser()
x = NextMethod()
return(x)
}
df <- as.data.frame(matrix(1:20, nrow=5))
class(df) <- c("MYCLASS","data.frame")
counttt
#[1] 9
But there's more. I tried to print the values of x in the method and got
really strange results
counttt <- 0
`[[.MYCLASS` = function(x, ...) {
counttt <<- counttt + 1
print(x)
# browser()
x = NextMethod()
return(x)
}
df <- as.data.frame(matrix(1:20, nrow=5))
class(df) <- c("MYCLASS","data.frame")
counttt
#[1] 151
If I change print to print.data.frame it goes up to
counttt
#[1] 176
With print.default back to 9. What is the print method called in the
second example?
sessionInfo()
R version 3.6.1 (2019-07-05)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 19.04
Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.8.0
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.8.0
locale:
[1] LC_CTYPE=pt_PT.UTF-8 LC_NUMERIC=C
[3] LC_TIME=pt_PT.UTF-8 LC_COLLATE=pt_PT.UTF-8
[5] LC_MONETARY=pt_PT.UTF-8 LC_MESSAGES=pt_PT.UTF-8
[7] LC_PAPER=pt_PT.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=pt_PT.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods
[7] base
loaded via a namespace (and not attached):
[1] sos_2.0-0 nlme_3.1-140 matrixStats_0.54.0
[4] fs_1.2.7 xts_0.11-2 usethis_1.5.0
[7] lubridate_1.7.4 devtools_2.0.2 RColorBrewer_1.1-2
[10] rprojroot_1.3-2 rbenchmark_1.0.0 tools_3.6.1
[13] backports_1.1.4 R6_2.4.0 rpart_4.1-15
[16] Hmisc_4.2-0 lazyeval_0.2.2 colorspace_1.4-1
[19] nnet_7.3-12 npsurv_0.4-0 withr_2.1.2
[22] tidyselect_0.2.5 gridExtra_2.3 prettyunits_1.0.2
[25] processx_3.3.0 curl_3.3 compiler_3.6.1
[28] cli_1.1.0 htmlTable_1.13.1 randomNames_1.4-0.0
[31] dvmisc_1.1.3 desc_1.2.0 tseries_0.10-46
[34] scales_1.0.0 checkmate_1.9.1 lmtest_0.9-36
[37] fracdiff_1.4-2 mvtnorm_1.0-10 quadprog_1.5-6
[40] callr_3.2.0 stringr_1.4.0 digest_0.6.18
[43] foreign_0.8-71 rio_0.5.16 base64enc_0.1-3
[46] stocks_1.1.4 pkgconfig_2.0.2 htmltools_0.3.6
[49] sessioninfo_1.1.1 readxl_1.3.1 htmlwidgets_1.3
[52] rlang_0.3.4 TTR_0.23-4 rstudioapi_0.10
[55] quantmod_0.4-14 MLmetrics_1.1.1 zoo_1.8-5
[58] zip_2.0.1 acepack_1.4.1 dplyr_0.8.0.1
[61] car_3.0-2 magrittr_1.5 Formula_1.2-3
[64] Matrix_1.2-17 Rcpp_1.0.1 munsell_0.5.0
[67] abind_1.4-5 stringi_1.4.3 forecast_8.6
[70] yaml_2.2.0 carData_3.0-2 MASS_7.3-51.3
[73] pkgbuild_1.0.3 plyr_1.8.4 grid_3.6.1
[76] parallel_3.6.1 forcats_0.4.0 crayon_1.3.4
[79] lattice_0.20-38 haven_2.1.0 splines_3.6.1
[82] hms_0.4.2 knitr_1.22 ps_1.3.0
[85] pillar_1.4.0 pkgload_1.0.2 urca_1.3-0
[88] glue_1.3.1 lsei_1.2-0 babynames_1.0.0
[91] latticeExtra_0.6-28 data.table_1.12.2 remotes_2.0.4
[94] cellranger_1.1.0 testthat_2.1.0 gtable_0.3.0
[97] purrr_0.3.2 assertthat_0.2.1 ggplot2_3.1.1
[100] openxlsx_4.1.0 xfun_0.6 survey_3.35-1
[103] survival_2.44-1.1 timeDate_3043.102 tibble_2.1.1
[106] memoise_1.1.0 cluster_2.0.8 toOrdinal_1.1-0.0
[109] fitdistrplus_1.0-14 brew_1.0-6
Hope this helps,
Rui Barradas
Às 13:16 de 15/07/19, Duncan Murdoch escreveu:
On 07/07/2019 11:49 a.m., Ghiggi Gionata wrote:
Hi all !
I noticed a strange behaviour of the function `class<-` when a
class-specific '[[.' method is defined.
Here below a reproducible example :
#-------------------------------------------------------------------.
counttt <- 0
`[[.MYCLASS` = function(x, ...) {
counttt <<- counttt + 1
# browser()
x = NextMethod()
return(x)
}
df <- as.data.frame(matrix(1:20, nrow=5))
class(df) <- c("MYCLASS","data.frame")
counttt
# The same occurs when using structure(, class=) or attr(,"class")<-
df <- as.data.frame(matrix(1:20, nrow=5))
df <- structure(df, class=c("MYCLASS","data.frame"))
attr(df, "class") <- c("MYCLASS","data.frame")
#-------------------------------------------------------------------.
Why in this example `class<-` is calling `[[.MYCLASS` 9 times ?
Is there a way to avoid `class<-` to call `[[.MYCLASS` ?
Thank you in advance for your help and suggestions.
This is what I see:
> counttt <- 0
>
> `[[.MYCLASS` = function(x, ...) {
+ counttt <<- counttt + 1
+ # browser()
+ x = NextMethod()
+ return(x)
+ }
>
> df <- as.data.frame(matrix(1:20, nrow=5))
> class(df) <- c("MYCLASS","data.frame")
> counttt
[1] 0
So there's something else going on in your system. Maybe post
sessionInfo()?
Duncan Murdoch
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