Direct label on smoothed line methods not working?

[markbneal]

Hi, I am trying to use the method as per this stackoverflow answer here

This code...

library("ggplot2")
#install.packages("directlabels")
library(directlabels)
set.seed(124234345)

# Generate data
df.2 <- data.frame("n_gram" = c("word1"),
                   "year" = rep(100:199),
                   "match_count" = runif(100 ,min = 1000 , max = 2000))

df.2 <- rbind(df.2, data.frame("n_gram" = c("word2"),
                               "year" = rep(100:199),
                               "match_count" = runif(100 ,min = 1000 , max = 2000)) )

# use stat smooth with geom_dl to get matching direct labels.
span <- 0.3
ggplot(df.2, aes(year, match_count, group=n_gram, color=n_gram)) +
  geom_line(alpha = I(7/10), color="grey") +
  stat_smooth(size=2, span=span, se=F) +
  geom_dl(aes(label=n_gram), method = "last.qp", stat="smooth", span=span) +
  xlim(c(100,220))+
  guides(colour="none")

produces this error:

Warning message:
Computation failed in `stat_smooth()`:
object 'last.qp' of mode 'function' was not found 

Interestingly, as a side issue, I went to run the code in the documentation from geom_dl() and i got fatal errors from Rstudio, when printing some objects, as noted in the code. I tested on Rstudio cloud, and that code worked fine there, but I'm running a pretty standard and neat setup - happy to give more details if this can't be reproduced.

#from geom_dl help
  vad <- as.data.frame.table(VADeaths)
  names(vad) <- c("age","demographic","deaths")
  ## color + legend
  leg <- ggplot(vad,aes(deaths,age,colour=demographic))+
    geom_line(aes(group=demographic))+
    xlim(8,80)
  print(direct.label(leg,list("last.points",rot=30)))
  ## this is what direct.label is doing internally:
  labeled <- leg+
    geom_dl(aes(label=demographic), method=list("last.points",rot=30))+
    scale_colour_discrete(guide="none")
  print(labeled)
  ## no color, just direct labels!
  p <- ggplot(vad,aes(deaths,age))+
    geom_line(aes(group=demographic))+
    geom_dl(aes(label=demographic),method="top.qp") #error when printing !!!!!!!!!!
  print(p)
  ## add color:
  p+aes(colour=demographic)+
    scale_colour_discrete(guide="none")
  ## add linetype:
  p+aes(linetype=demographic)+
    scale_linetype(guide="none")
  ## no color, just direct labels
  library(nlme)
  bwbase <- ggplot(BodyWeight,aes(Time,weight,label=Rat))+
    geom_line(aes(group=Rat))+
    facet_grid(.~Diet)
  bw <- bwbase+geom_dl(method="last.qp") #error when printing !!!!!!!!!!
  print(bw)
  ## add some more direct labels
  bw2 <- bw+geom_dl(method="first.qp")
  print(bw2)
  ## add color
  colored <- bw2+aes(colour=Rat)+
    scale_colour_discrete(guide="none")
  print(colored)
  ## or just use direct.label if you use color:
  direct.label(bwbase+aes(colour=Rat),dl.combine("first.qp","last.qp"))
  
  ## iris data example
  giris <- ggplot(iris,aes(Petal.Length,Sepal.Length))+
    geom_point(aes(shape=Species))
  giris.labeled <- giris+
    geom_dl(aes(label=Species),method="smart.grid")+
    scale_shape_manual(values=c(setosa=1,virginica=6,versicolor=3),
                       guide="none")
  ##png("~/R/directlabels/www/scatter-bw-ggplot2.png",h=503,w=503)
  print(giris.labeled)
  ##dev.off()

[markbneal]

Sessioninfo()

R version 3.6.1 (2019-07-05)
Platform: i386-w64-mingw32/i386 (32-bit)
Running under: Windows 10 x64 (build 18363)

Matrix products: default

locale:
[1] LC_COLLATE=English_New Zealand.1252  LC_CTYPE=English_New Zealand.1252    LC_MONETARY=English_New Zealand.1252
[4] LC_NUMERIC=C                         LC_TIME=English_New Zealand.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] directlabels_2020.1.31 ggplot2_3.3.0         

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.3       rstudioapi_0.11  magrittr_1.5     splines_3.6.1    tidyselect_1.0.0 munsell_0.5.0    lattice_0.20-40 
 [8] colorspace_1.4-1 R6_2.4.1         rlang_0.4.5      quadprog_1.5-8   dplyr_0.8.4      tools_3.6.1      ggpmisc_0.3.3   
[15] grid_3.6.1       packrat_0.5.0    gtable_0.3.0     nlme_3.1-144     mgcv_1.8-31      withr_2.1.2      digest_0.6.25   
[22] assertthat_0.2.1 tibble_2.1.3     lifecycle_0.2.0  crayon_1.3.4     Matrix_1.2-18    farver_2.0.3     purrr_0.3.3     
[29] glue_1.3.1       labeling_0.3     compiler_3.6.1   pillar_1.4.3     scales_1.1.0     pkgconfig_2.0.3 

[tdhock]

this issue happens because stat_smooth also has a "method" parameter. the method="last.qp" is meant to be passed to geom_dl, but ggplot2 (mistakenly?) passes it to stat_smooth, which rightly raises the warning because it does not know anything about last.qp.
I posted an issue with ggplot2 tidyverse/ggplot2#4073 so maybe they will suggest a fix.
BTW in 2013 at the time of my SO answer this was working, but ggplot2 changed something (how the extra params/arguments are handled?) so that now it no longer works.

[tdhock]

a work-around with the current code is to calculate the smooth yourself (instead of using stat_smooth), save the smooth lines in a data table, and then plot/label it via geom_line/geom_dl.

[tdhock]

another work-around is mentioned in tidyverse/ggplot2#4073 (comment) and this seems to be an issue with ggplot2 so I'm closing this issue.