A Bollinger Bands chart displays price data with a volatility envelope consisting of three lines: a middle band (simple moving average), an upper band (SMA plus 2 standard deviations), and a lower band (SMA minus 2 standard deviations). This technical indicator helps traders identify overbought/oversold conditions, volatility patterns, and potential price breakouts by showing how prices relate to their recent statistical range.
# anyplot.ai
# indicator-bollinger: Bollinger Bands Indicator Chart
# Library: makie 0.21.9 | Julia 1.11.9
# Quality: 95/100 | Created: 2026-09-02
using CairoMakie
using Colors
using Random
using Statistics
using Dates
Random.seed!(42)
# --- Theme tokens -------------------------------------------------------
THEME = get(ENV, "ANYPLOT_THEME", "light")
PAGE_BG = THEME == "light" ? colorant"#FAF8F1" : colorant"#1A1A17"
INK = THEME == "light" ? colorant"#1A1A17" : colorant"#F0EFE8"
INK_SOFT = THEME == "light" ? colorant"#4A4A44" : colorant"#B8B7B0"
# Imprint categorical palette — first series ALWAYS brand green
IMPRINT_PALETTE = [
colorant"#009E73", # 1 — brand green (price line)
colorant"#C475FD", # 2 — lavender (band envelope + band-width panel)
colorant"#4467A3", # 3 — blue
colorant"#BD8233", # 4 — ochre
colorant"#AE3030", # 5 — matte red
colorant"#2ABCCD", # 6 — cyan
colorant"#954477", # 7 — rose
colorant"#99B314", # 8 — lime
]
# --- Data -----------------------------------------------------------------
# Daily closing prices for a 120-trading-day window, with an engineered
# volatility squeeze followed by a breakout to demonstrate band behavior.
n_days = 120
window = 20
trading_dates = Date[]
current_date = Date(2024, 1, 2)
while length(trading_dates) < n_days
if Dates.dayofweek(current_date) <= 5
push!(trading_dates, current_date)
end
global current_date += Day(1)
end
calm_returns = randn(45) .* 2.2
squeeze_returns = randn(35) .* 0.6
breakout_returns = randn(n_days - 80) .* 2.8 .+ 0.9
daily_returns = vcat(calm_returns, squeeze_returns, breakout_returns)
close_price = 150.0 .+ cumsum(daily_returns)
trading_day = 1:n_days
band_range = window:n_days
sma = [mean(close_price[(i - window + 1):i]) for i in band_range]
band_std = [std(close_price[(i - window + 1):i]) for i in band_range]
upper_band = sma .+ 2 .* band_std
lower_band = sma .- 2 .* band_std
# --- Plot -------------------------------------------------------------------
fig = Figure(
resolution = (1600, 900),
fontsize = 14,
backgroundcolor = PAGE_BG,
)
ax_price = Axis(
fig[1, 1];
title = "indicator-bollinger · julia · makie · anyplot.ai",
titlesize = 20,
titlecolor = INK,
ylabel = "Price (USD)",
ylabelsize = 14,
ylabelcolor = INK,
yticklabelsize = 12,
yticklabelcolor = INK_SOFT,
ytickcolor = INK_SOFT,
xticksvisible = false,
xticklabelsvisible = false,
backgroundcolor = PAGE_BG,
topspinevisible = false,
rightspinevisible = false,
leftspinecolor = INK_SOFT,
bottomspinecolor = INK_SOFT,
xgridvisible = false,
ygridcolor = RGBAf(INK.r, INK.g, INK.b, 0.15),
yminorgridvisible = false,
)
# Linked sub-panel: band width (upper - lower) makes the volatility
# squeeze/breakout pattern explicit instead of leaving it implicit in the
# envelope's visual width alone.
ax_width = Axis(
fig[2, 1];
xlabel = "Date",
ylabel = "Band width",
xlabelsize = 14,
ylabelsize = 14,
xlabelcolor = INK,
ylabelcolor = INK,
xticklabelsize = 12,
yticklabelsize = 12,
xticklabelcolor = INK_SOFT,
yticklabelcolor = INK_SOFT,
xtickcolor = INK_SOFT,
ytickcolor = INK_SOFT,
backgroundcolor = PAGE_BG,
topspinevisible = false,
rightspinevisible = false,
leftspinecolor = INK_SOFT,
bottomspinecolor = INK_SOFT,
xgridvisible = false,
ygridcolor = RGBAf(INK.r, INK.g, INK.b, 0.15),
yminorgridvisible = false,
)
linkxaxes!(ax_price, ax_width)
tick_positions = 1:15:n_days
ax_width.xticks = (tick_positions, Dates.format.(trading_dates[tick_positions], "u d"))
band_plot = band!(
ax_price, band_range, lower_band, upper_band;
color = (IMPRINT_PALETTE[2], 0.18),
)
lines!(ax_price, band_range, upper_band; color = IMPRINT_PALETTE[2], linewidth = 1.5)
lines!(ax_price, band_range, lower_band; color = IMPRINT_PALETTE[2], linewidth = 1.5)
sma_line = lines!(ax_price, band_range, sma; color = INK, linestyle = :dash, linewidth = 2)
close_line = lines!(
ax_price, trading_day, close_price;
color = IMPRINT_PALETTE[1], linewidth = 3,
)
band_width = upper_band .- lower_band
lines!(ax_width, band_range, band_width; color = IMPRINT_PALETTE[2], linewidth = 2)
Legend(
fig[1:2, 2],
[close_line, sma_line, band_plot],
["Close price", "20-day SMA", "Bands (±2σ)"];
framevisible = false,
labelcolor = INK,
backgroundcolor = :transparent,
)
rowsize!(fig.layout, 1, Relative(0.68))
rowsize!(fig.layout, 2, Relative(0.32))
colsize!(fig.layout, 1, Relative(0.86))
# --- Save -------------------------------------------------------------------
save("plot-$(THEME).png", fig; px_per_unit = 2)
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/indicator-bollinger/makie/code. Any spec id and library id listed in llms-full.txt fit the same URL shape; every URL below is complete and callable.
{
"spec_id": "indicator-bollinger",
"language": "julia",
"library": "makie",
"page": "https://anyplot.ai/indicator-bollinger/julia/makie",
"hub": "https://anyplot.ai/indicator-bollinger",
"code_json": "https://api.anyplot.ai/specs/indicator-bollinger/makie/code",
"spec_json": "https://api.anyplot.ai/specs/indicator-bollinger",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/indicator-bollinger/julia/makie/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/indicator-bollinger/julia/makie/plot-dark.png",
"quality_score": 95.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Bollinger Bands Indicator Chart on anyplot.ai.