ggerrorplot: add option to treat x as numeric axis

[kassambara]

The current default of ggerrorplot() is to always treat x as a factor.

The option numeric.x.axis should be added; logical value. If TRUE, x axis will be treated as numeric. Default is FALSE.

[kassambara]

suppressPackageStartupMessages(library(ggpubr))

# Demo data
mi_df <- data.frame(
  "month" = as.numeric(rep(c(0,1,2,12,15,48),30)) , 
  "sust" = as.factor(rep(c(rep(c("A","B"), each=6)), 15)),
  "vble" = as.numeric(rnorm(180)))

# Error plot: x-axis treated as factor (default)
ggerrorplot(
  mi_df, x = "month", y = "vble", 
  desc_stat = "mean_sd", color = "sust", palette = c("black","grey"),
  title= "smt", ylab= "vble",             
  position = position_dodge(0.3)   
  )

# Using numeric x axis: numeric.x.axis = TRUE
ggerrorplot(
  mi_df, x = "month", y = "vble", 
  desc_stat = "mean_sd", color = "sust", palette = c("black","grey"),
  title= "smt", ylab= "vble",             
  position = position_dodge(0.3),
  numeric.x.axis = TRUE
)

^{Created on 2020-05-24 by the reprex package (v0.3.0.9001)}