Error messages

[jtrakk]

When Gadfly.plot() fails, it displays Plot(...) but that doesn't help me figure out what's wrong. It would be great if I could get some helpful diagnostic messages when the plotting fails.

[Mattriks]

Try e.g. draw(PNG(), p) where p is a plot. In the Gadfly docs, see Backends.

[jtrakk]

Thanks, that works.

p = plot(DataFrame(a=[1,2,3], b=[missing,20,30]), Geom.point(), x=:a, y=:b)

just gives Plot(...).

p = plot(DataFrame(a=[1,2,3], b=[missing,20,30]), Geom.point(), x=:a, y=:b)
draw(PNG(),p)

shows

MethodError: no method matching *(::Missing, ::Measures.Length{:mm,Float64})

In Jupyter,

plot(DataFrame(a=[1,2,3], b=[10,20,30]), Geom.point(), x=:a, y=:b)

successfully displays a scatterplot without explicitly specifying a backend, but when it fails (in the missing case), there's no error message, only Plot(...) unless I explicitly call draw(PNG(), p).

Would it be a good idea to give errors for failing plots in Jupyter without explicitly calling draw(PNG(), p)?

[Mattriks]

What version of Gadfly do you have? ]st Gadfly Your example works for me on Gadfly 1.3.1

[jtrakk]

1.3.0

[Mattriks]

Yep general support for missing got added to Gadfly in #1459 (by updating Compose to v0.9). #1459 was merged between Gadfly v1.3 and v1.3.1. So you need to upgrade.

[jtrakk]

That's good to know. It would still be nice for the error messages to appear without needing to specify a backend.

[tlnagy]

It would still be nice for the error messages to appear without needing to specify a backend.

Agreed. Do we know why the error messages get hidden behind Plot(...) seems like a bug in the display code.