Styling Markers in Julia
How to style markers in Julia with Plotly.
Add Marker Border
In order to make markers look more distinct, you can add a border to the markers. This can be achieved by adding the line property to the marker object.
Here is an example of adding a marker border to a faceted scatter plot created using Plotly Express.
using PlotlyJS, CSV, DataFrames
df = dataset(DataFrame, "iris")
plot(
df, x=:sepal_width, y=:sepal_length, color=:species, mode="markers",
marker=attr(size=12, line=attr(width=2, color="DarkSlateGrey"))
)Here is an example that creates an empty graph object figure, and then adds two scatter traces with a marker border.
using PlotlyJS, Distributions
# Generate example data
x = rand(Uniform(3,6), 500)
y = rand(Uniform(3,6), 500)
# Add scatter trace with medium sized markers
trace1 = scatter(
mode="markers",
x=x,
y=y,
marker=attr(
color="LightSkyBlue",
size=20,
line=attr(
color="MediumPurple",
width=2
)
),
showlegend=false
)
# Add trace with large marker
trace2 = scatter(
mode="markers",
x=[2],
y=[4.5],
marker=attr(
color="LightSkyBlue",
size=120,
line=attr(
color="MediumPurple",
width=12
)
),
showlegend=false
)
plot([trace1, trace2])
Fully opaque, the default setting, is useful for non-overlapping markers. When many points overlap it can be hard to observe density.
Opacity
Setting opacity outside the marker will set the opacity of the trace. Thus, it will allow greater visibility of additional traces but like fully opaque it is hard to distinguish density.
using PlotlyJS, Distributions
# Generate example data
x = rand(Uniform(3, 6), 500)
y = rand(Uniform(3, 4.5), 500)
x2 = rand(Uniform(3, 6), 500)
y2 = rand(Uniform(4.5, 6), 500)
# Add first scatter trace with medium sized markers
trace1 = scatter(
mode="markers",
x=x,
y=y,
opacity=0.5,
marker=attr(
color="LightSkyBlue",
size=20,
line=attr(
color="MediumPurple",
width=2
)
),
name="Opacity 0.5"
)
# Add second scatter trace with medium sized markers
# and opacity 1.0
trace2 = scatter(
mode="markers",
x=x2,
y=y2,
marker=attr(
color="LightSkyBlue",
size=20,
line=attr(
color="MediumPurple",
width=2
)
),
name="Opacity 1.0"
)
# Add trace with large markers
trace3 = scatter(
mode="markers",
x=[2, 2],
y=[4.25, 4.75],
opacity=0.5,
marker=attr(
color="LightSkyBlue",
size=80,
line=attr(
color="MediumPurple",
width=8
)
),
showlegend=false
)
plot([trace1, trace2, trace3])Marker Opacity
To maximise visibility of density, it is recommended to set the opacity inside the marker marker:{opacity:0.5}. If multiple traces exist with high density, consider using marker opacity in conjunction with trace opacity.
using PlotlyJS, Distributions
# Generate example data
x = rand(Uniform(3, 6),500)
y = rand(Uniform(3, 6),500)
# Add scatter trace with medium sized markers
trace1 = scatter(
mode="markers",
x=x,
y=y,
marker=attr(
color="LightSkyBlue",
size=20,
opacity=0.5,
line=attr(
color="MediumPurple",
width=2
)
),
showlegend=false
)
# Add trace with large markers
trace2 =scatter(
mode="markers",
x=[2, 2],
y=[4.25, 4.75],
marker=attr(
color="LightSkyBlue",
size=80,
opacity=0.5,
line=attr(
color="MediumPurple",
width=8
)
),
showlegend=false
)
plot([trace1, trace2])Color Opacity
To maximise visibility of each point, set the color as an rgba string that includes an alpha value of 0.5.
This example sets the marker color to 'rgba(135, 206, 250, 0.5)'. The rgb values of 135, 206, and 250 are from the definition of the LightSkyBlue named CSS color that is is used in the previous examples (See https://www.color-hex.com/color/87cefa). The marker line will remain opaque.
using PlotlyJS, Distributions
# Generate example data
x = rand(Uniform(3, 6),500)
y = rand(Uniform(3, 6),500)
# Add scatter trace with medium sized markers
trace1 = scatter(
mode="markers",
x=x,
y=y,
marker=attr(
color="rgba(135, 206, 250, 0.5)",
size=20,
line=attr(
color="MediumPurple",
width=2
)
),
showlegend=false
)
# Add trace with large markers
trace2 = scatter(
mode="markers",
x=[2, 2],
y=[4.25, 4.75],
marker=attr(
color="rgba(135, 206, 250, 0.5)",
size=80,
line=attr(
color="MediumPurple",
width=8
)
),
showlegend=false
)
plot([trace1, trace2])
Custom Marker Symbols
The marker_symbol attribute allows you to choose from a wide array of symbols to represent markers in your figures.
The basic symbols are: circle, square, diamond, cross, x, triangle, pentagon, hexagram, star, diamond, hourglass, bowtie, asterisk, hash, y, and line.
Each basic symbol is also represented by a number. Adding 100 to that number is equivalent to appending the suffix "-open" to a symbol name. Adding 200 is equivalent to appending "-dot" to a symbol name. Adding 300 is equivalent to appending "-open-dot" or "dot-open" to a symbol name.
In the following figure, hover over a symbol to see its name or number. Set the marker_symbol attribute equal to that name or number to change the marker symbol in your figure.
raw_symbols = PlotlyBase.get_plotschema().traces[:scatter][:attributes][:marker][:symbol][:values]
namestems = []
namevariants = []
symbols = []
for i in 1:3:length(raw_symbols)
name = raw_symbols[i+2]
namestem = replace(replace(name, "-open" => ""), "-dot" => "")
push!(symbols, raw_symbols[i])
push!(namestems, namestem)
push!(namevariants, name[(length(namestem)+1):end])
end
trace = scatter(
x=namevariants, y=namestems, mode="markers",
marker=attr(
symbol=symbols,
line=attr(width=2, color="midnightblue"),
color="lightskyblue", size=15
),
hovertemplate="name: %{y}%{x}<br>number: %{marker.symbol}<extra></extra>"
)
layout = Layout(
title="Mouse over symbols for name & number!",
xaxis_range=[-1,4], yaxis_range=[length(unique(namestems)),-1],
margin=attr(b=0,r=0), xaxis_side="top", height=1400, width=400
)
plot([trace], layout)Reference
See https://plotly.com/julia/reference/ for more information and chart attribute options!