njtierney/naniar

geom_missing_point renders points cropped by plot limits as 'Missing'

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#58 opened on Jun 15, 2017

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bugenhancementhelp wanted

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Description

@karawoo's response to my ggplot2 issue on missing data warnings made me twig this behaviour could also be an issue for geom_missing_point. It turns out that converting data outside the plot limits to NA seems to happen before our overloaded setup_data...(wat) creating a potentially misleading plot:

library(narnia)
library(ggplot2)
df <- data.frame(x = c(1:5) , y = 1:5)

ggplot(df, aes(x = x, y = y)) + 
  geom_missing_point() +
  xlim(c(0,4)) +
  ylim(c(0,5))

Her proposed work around using coord_cartesian does avoid the incorrect point categorisation:

ggplot(df, aes(x = x, y = y)) +                
geom_missing_point() +                         
coord_cartesian(xlim = c(0, 4), ylim = c(0, 5))

Contributor guide

Research direction
Investigate the order of operations in geom missing point's setup data method. The issue is that data outside plot limits is converted to NA before setup data runs, causing misclassification. Look at how ggplot2 handles limits and when NA conversion occurs. Potential fix: use coord cartesian or modify setup data to run after NA conversion.
Tech stack
r
Domain
data visualization
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Rggplot2
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
55