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Indicators in Julia

How to make gauge charts in Julia with Plotly.


Overview

In this tutorial we introduce a new trace named "Indicator". The purpose of "indicator" is to visualize a single value specified by the "value" attribute. Three distinct visual elements are available to represent that value: number, delta and gauge. Any combination of them can be specified via the "mode" attribute. Top-level attributes are:

  1. value: the value to visualize

  2. mode: which visual elements to draw

  3. align: how to align number and delta (left, center, right)

  4. domain: the extent of the figure

Then we can configure the 3 different visual elements via their respective container:

  1. number is simply a representation of the number in text. It has attributes:

  2. valueformat: to format the number

  3. prefix: a string before the number

  4. suffix: a string after the number

  5. font.(family|size): to control the font

"delta" simply displays the difference between the value with respect to a reference. It has attributes:

  1. reference: the number to compare the value with

  2. relative: whether that difference is absolute or relative

  3. valueformat: to format the delta

  4. (increasing|decreasing).color: color to be used for positive or decreasing delta

  5. (increasing|decreasing).symbol: symbol displayed on the left of the delta

  6. font.(family|size): to control the font

  7. position: position relative to number (either top, left, bottom, right)

Finally, we can have a simple title for the indicator via title with 'text' attribute which is a string, and 'align' which can be set to left, center, and right. There are two gauge types: angular and bullet. Here is a combination of both shapes (angular, bullet), and different modes (gauge, delta, and value):

using PlotlyJS


trace1 = indicator(
    value=200,
    delta_reference=160,
    gauge_axis_visible=false,
    domain=attr(row=0, column=0)
)

trace2 = indicator(
    value=120,
    gauge=attr(shape="bullet", axis=_visible=false),
    domain=attr(x=[0.05, 0.5], y=[0.15, 0.35])
)

trace3 = indicator(
    mode="number+delta",
    value=300,
    domain=attr(row=0, column=1)
)

trace4 = indicator(
    mode="delta",
    value=40,
    domain=attr(row=1, column=1)
)

layout = Layout(
    grid=attr(rows=2, columns=2, pattern="independent"),
    template=Template(data=attr(
        indicator=[attr(
            title_text="Speed",
            mode="number+delta+gauge",
            delta_reference=90
        )]
    ))
)
plot([trace1, trace2, trace3, trace4], layout)

A Single Angular Gauge Chart

using PlotlyJS

plot(indicator(
    mode="gauge+number",
    value=450,
    title=attr(text="Speed"),
    domain=attr(x=[0, 1], y=[0, 1])
))
Bullet Gauge

The equivalent of above "angular gauge":

using PlotlyJS

plot(indicator(
    mode="number+gauge+delta",
    gauge=attr(shape="bullet"),
    delta=attr(reference=300),
    value=220,
    domain=attr(x=[0.1, 1], y=[0.2, 0.9]),
    title=attr(text="Avg order size")
))

Showing Information above Your Chart

Another interesting feature is that indicator trace sits above the other traces (even the 3d ones). This way, it can be easily used as an overlay as demonstrated below

using PlotlyJS

trace = indicator(
    mode="number+delta",
    value=492,
    delta=attr(reference=512, valueformat=".0f"),
    title_text="Users online",
    domain=attr(y=[0, 1], x=[0.25, 0.75])
)

trace2 = scatter(
    y=[325, 324, 405, 400, 424, 404, 417, 432, 419, 394, 410, 426, 413, 419, 404, 408, 401, 377, 368, 361, 356, 359, 375, 397, 394, 418, 437, 450, 430, 442, 424, 443, 420, 418, 423, 423, 426, 440, 437, 436, 447, 460, 478, 472, 450, 456, 436, 418, 429, 412, 429, 442, 464, 447, 434, 457, 474, 480, 499, 497, 480, 502, 512, 492])

layout = Layout(xaxis_range=[0, 62])
plot([trace, trace2], layout)

Data Cards / Big Numbers

Data card helps to display more contextual information about the data. Sometimes one number is all you want to see in a report, such as total sales, annual revenue, etc. This example shows how to visualize these big numbers:

using PlotlyJS

trace1 = indicator(
    mode="number+delta",
    value=400,
    number=_prefix="\$",
    delta=attr(position="top", reference=320),
    domain=attr(x=[0, 1], y=[0, 1])
)

layout = Layout(paper_bgcolor="lightgray")

plot(trace1, layout)

It's possible to display several numbers

using PlotlyJS

trace1 = indicator(
    mode="number+delta",
    value=200,
    domain=attr(x=[0, 0.5], y=[0, 0.5]),
    delta=attr(reference=400, relative=true, position="top")
)

trace2 = indicator(
    mode="number+delta",
    value=350,
    delta=attr(reference=400, relative=true),
    domain=attr(x=[0, 0.5], y=[0.5, 1])
)

trace3 = indicator(
    mode="number+delta",
    value=450,
    title_text="Accounts<br><span style='font-size:0.8em;color:gray'>Subtitle</span><br><span style='font-size:0.8em;color:gray'>Subsubtitle</span>",
    delta=attr(reference=400, relative=true),
    domain=attr(x=[0.6, 1], y=[0, 1])
)

plot([trace1, trace2, trace3])

Reference

See https://plotly.com/julia/reference/indicator/ for more information and chart attribute options!