Edge colours interpreted literally when ggraph is not loaded

[lazappi]

Hi

Possibly this is known behaviour but just thought I would report it in case it wasn't. When you try to
colour edges using a numeric variable without loading ggraph the values are interpreted as literal colours rather than continuous numeric values.

Toy example graph:

library(tidygraph)
#> Warning: package 'tidygraph' was built under R version 4.0.2
#> 
#> Attaching package: 'tidygraph'
#> The following object is masked from 'package:stats':
#> 
#>     filter

nodes <- data.frame(
    node = c(1, 2, 3, 4)
)

edges <- data.frame(
    from   = c(1, 2, 2),
    to     = c(2, 3, 4),
    weight = c(5, 3, 2)
)

graph <- tbl_graph(nodes = nodes, edges = edges)

If we plot this without loading ggraph we get three distinct colours for the edges:

ggraph::ggraph(graph, layout = "fr") +
    ggraph::geom_edge_link(ggplot2::aes(colour = weight)) +
    ggraph::geom_node_point()

I think they are being interpreted as literal colours rather than a factor because if you change the weights the colours change and if you give a negative weight you get his error:

ggraph::ggraph(graph, layout = "fr") +
    ggraph::geom_edge_link(ggplot2::aes(colour = -weight)) +
    ggraph::geom_node_point()
#> Error: colours encodes as numbers must be positive

If we load ggraph we get a continuous colour scale as expected:

library(ggraph)
#> Loading required package: ggplot2

ggraph(graph, layout = "fr") +
    geom_edge_link(aes(colour = weight)) +
    geom_node_point()

^{Created on 2021-02-01 by the reprex package (v0.3.0)}

Session info

sessionInfo()
#> R version 4.0.0 (2020-04-24)
#> Platform: x86_64-apple-darwin17.0 (64-bit)
#> Running under: macOS Catalina 10.15.7
#> 
#> Matrix products: default
#> BLAS:   /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRblas.dylib
#> LAPACK: /Library/Frameworks/R.framework/Versions/4.0/Resources/lib/libRlapack.dylib
#> 
#> locale:
#> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
#> 
#> attached base packages:
#> [1] stats     graphics  grDevices utils     datasets  methods   base     
#> 
#> other attached packages:
#> [1] ggraph_2.0.4    ggplot2_3.3.3   tidygraph_1.2.0
#> 
#> loaded via a namespace (and not attached):
#>  [1] Rcpp_1.0.5         pillar_1.4.7       compiler_4.0.0     highr_0.8         
#>  [5] viridis_0.5.1      tools_4.0.0        digest_0.6.27      viridisLite_0.3.0 
#>  [9] evaluate_0.14      lifecycle_0.2.0    tibble_3.0.4       gtable_0.3.0      
#> [13] pkgconfig_2.0.3    rlang_0.4.10       igraph_1.2.6       curl_4.3          
#> [17] ggrepel_0.9.0      yaml_2.2.1         xfun_0.20          gridExtra_2.3     
#> [21] xml2_1.3.2         httr_1.4.2         withr_2.3.0        dplyr_1.0.2       
#> [25] stringr_1.4.0      knitr_1.30         graphlayouts_0.7.1 generics_0.1.0    
#> [29] vctrs_0.3.6        grid_4.0.0         tidyselect_1.1.0   glue_1.4.2        
#> [33] R6_2.5.0           rmarkdown_2.6      polyclip_1.10-0    farver_2.0.3      
#> [37] purrr_0.3.4        tidyr_1.1.2        tweenr_1.0.1       magrittr_2.0.1    
#> [41] scales_1.1.1       ellipsis_0.3.1     htmltools_0.5.0    MASS_7.3-53       
#> [45] mime_0.9           ggforce_0.3.2      colorspace_2.0-0   labeling_0.4.2    
#> [49] stringi_1.5.3      munsell_0.5.0      crayon_1.3.4

[thomasp85]

This is a known issue that is caused by how ggplot2 figures out scales. Unfortunately there is nothing we can do from ggraphs side on this