Putting it Together

We will now look at how to combine traces and a layout to create a plot.

We'll also discuss how to integrate with various frontends.

Plot

Recall that the definition of the Plot object is

mutable struct Plot{TT<:AbstractVector{<:AbstractTrace},TL<:AbstractLayout,TF<:AbstractVector{<:PlotlyFrame}}
    data::TT
    layout::TL
    frames::TF
    divid::UUID
    config::PlotConfig
end

Given one or more AbstractTraces and optionally a Layout, we construct a Plot object with any of the following constructors

# A blank canvas no traces or a layout
Plot()

# A vector of traces and a layout
Plot{T<:AbstractTrace}(data::AbstractVector{T}, layout::AbstractLayout)

# A vector of traces -- default layout supplied
Plot{T<:AbstractTrace}(data::AbstractVector{T})

# a single trace: will be put into a vector -- default layout supplied
Plot(data::AbstractTrace)

# a single trace and a layout (trace put into a vector)
Plot(data::AbstractTrace, layout::AbstractLayout)

Notice that none of the recommended constructors have you pass the divid field manually. This is an internal field used to allow the display and unique identification of multiple plots in a single web page.

Convenience methods

There are also a number of convenience methods to the Plot function that will attempt to construct the traces for you. They have the following signatures

Plot(x, y; ...)
Plot(x, y, l; kind, config, kwargs...)

Plot(y; ...)
Plot(y, l; kwargs...)

Plot(f, x0, x1; ...)
Plot(f, x0, x1, l; config, kwargs...)

Plot(fs, x0, x1; ...)
Plot(fs, x0, x1, l; config, kwargs...)

Plot(df; ...)
Plot(
    df,
    l;
    category_orders,
    labels,
    facet_row,
    facet_row_wrap,
    facet_col,
    facet_col_wrap,
    group,
    symbol,
    color,
    line_dash,
    kw...
)

Plot(d, x, y; ...)
Plot(d, x, y, l; kwargs...)

Plot(d, y; ...)
Plot(d, y, l; kwargs...)

Especially convenient is the group keyword argument when calling Plot(::AbstractDataFrame, ... ; ...). Here is an example below:

using RDatasets
iris = RDatasets.dataset("datasets", "iris");
p = Plot(iris, x=:SepalLength, y=:SepalWidth, mode="markers", marker_size=8, group=:Species)

SyncPlots

A Plot is a pure Julia object and doesn't interact with plotly.js by itself. This means that we can't view the actual plotly figure the data represents.

To do that we need to link the Plot to one or more display frontends.

To actually connect to the display frontends we use the WebIO.jl package. Our interaction with WebIO is wrapped up in a type called SyncPlot that is defined as follows:

mutable struct SyncPlot
    plot::PlotlyBase.Plot
    scope::Scope
    window::Union{Nothing,Blink.Window}
end

As its name suggests, a SyncPlot will keep the Julia representation of the a plot (the Plot instance) in sync with a plot with a frontend.

By leveraging WebIO.jl we can render our figures anywhere WebIO can render. At time of writing this includes Jupyter notebooks, Jupyterlab, Mux.jl web apps, the Juno Julia environment inside the Atom text editor, and Electron windows from Blink.jl. Please see the WebIO.jl readme for additional (and up to date!) information.

When using PlotlyJS.jl at the Julia REPL a plot will automatically be displayed in an Electron window. This is a dedicated browser window we have full control over. To see a plot p, just type p by itself at the REPL and execute the line. Alternatively you can call display(p).

In addition to being able to see our charts in many front-end environments, WebIO also provides a 2-way communication bridge between javascript and Julia. In fact, when a SyncPlot is constructed, we automatically get listeners for all plotly.js javascript events. What's more is that we can hook up Julia functions as callbacks when those events are triggered. In the very contrived example below we have Julia print out details regarding points on a plot whenever a user hovers over them on the display:

using WebIO
p = plot(rand(10, 4));
display(p)  # usually optional

on(p["hover"]) do data
    println("\nYou hovered over", data)
end

In this next example, whenever we click on a point we change its marker symbol to a star and marker color to gold:

using WebIO
colors = (fill("red", 10), fill("blue", 10))
symbols = (fill("circle", 10), fill("circle", 10))
ys = (rand(10), rand(10))
p = plot(
    [scatter(y=y, marker=attr(color=c, symbol=s, size=15), line_color=c[1])
    for (y, c, s) in zip(ys, colors, symbols)]
)
display(p)  # usually optional

on(p["click"]) do data
    colors = (fill("red", 10), fill("blue", 10))
    symbols = (fill("circle", 10), fill("circle", 10))
    for point in data["points"]
        colors[point["curveNumber"] + 1][point["pointIndex"] + 1] = "gold"
        symbols[point["curveNumber"] + 1][point["pointIndex"] + 1] = "star"
    end
    restyle!(p, marker_color=colors, marker_symbol=symbols)
end

While completely nonsensical, hopefully these examples show you that it is possible to build rich, interactive, web-based data visualization applications with business logic implemented entirely in Julia!.

Display configuration

When calling plot or Plot, we can specify some configuration options using the config keyword argument.

The config argument must be set to an instance of PlotConfig, which should be constructed using keyword arguments.

As an example, if we were to execute the following code, we would see a static chart (no hover information or ability to zoom/pan) with 4 lines instead of an interactive one:

Plot(rand(10, 4), config=PlotConfig(staticPlot=true))

See the API docs for PlotConfig for a full list of options.