A forest plot displays effect sizes with confidence intervals from multiple studies in a meta-analysis. Each study is represented as a point estimate with horizontal whiskers showing the confidence interval, and a diamond at the bottom shows the pooled estimate. The plot includes a vertical reference line at the null effect (typically 0 or 1), making it easy to assess statistical significance and heterogeneity across studies.
// anyplot.ai
// forest-basic: Meta-Analysis Forest Plot
// Library: chartjs 4.4.7 | JavaScript 22.23.2
// Quality: 92/100 | Created: 2026-09-05
const t = window.ANYPLOT_TOKENS;
const MUTED = window.ANYPLOT_THEME === "dark" ? "#A8A79F" : "#6B6A63";
// --- Data (in-memory, deterministic) ----------------------------------------
// Meta-analysis of 11 randomized controlled trials comparing a new therapy
// against placebo on treatment response (odds ratio > 1 favors the therapy).
const studies = [
{ study: "Anderson 2014", effect: 1.35, ciLower: 0.82, ciUpper: 2.22, weight: 5.4 },
{ study: "Bianchi 2015", effect: 1.62, ciLower: 1.05, ciUpper: 2.5, weight: 6.8 },
{ study: "Castillo 2016", effect: 0.95, ciLower: 0.58, ciUpper: 1.56, weight: 5.1 },
{ study: "Dubois 2017", effect: 1.88, ciLower: 1.2, ciUpper: 2.94, weight: 7.2 },
{ study: "Eriksson 2018", effect: 1.41, ciLower: 1.02, ciUpper: 1.95, weight: 11.5 },
{ study: "Fujimoto 2018", effect: 2.05, ciLower: 1.18, ciUpper: 3.56, weight: 4.6 },
{ study: "Gupta 2019", effect: 1.22, ciLower: 0.88, ciUpper: 1.69, weight: 10.3 },
{ study: "Haddad 2020", effect: 1.55, ciLower: 1.15, ciUpper: 2.09, weight: 12.7 },
{ study: "Ivanov 2021", effect: 1.1, ciLower: 0.71, ciUpper: 1.7, weight: 6.9 },
{ study: "Jensen 2022", effect: 1.78, ciLower: 1.28, ciUpper: 2.48, weight: 9.8 },
{ study: "Kowalski 2023", effect: 1.48, ciLower: 1.18, ciUpper: 1.86, weight: 19.7 },
];
const pooled = { study: "Pooled Effect", effect: 1.45, ciLower: 1.28, ciUpper: 1.65 };
const nullEffect = 1;
const labels = [...studies.map((s) => s.study), pooled.study];
// --- Mount -------------------------------------------------------------------
const canvas = document.createElement("canvas");
document.getElementById("container").appendChild(canvas);
// --- Chart --------------------------------------------------------------------
const title = "forest-basic · javascript · chartjs · anyplot.ai";
new Chart(canvas, {
type: "bar",
data: {
labels,
datasets: [
{
label: "Null effect (OR = 1)",
type: "line",
data: labels.map((label) => ({ x: nullEffect, y: label })),
borderColor: MUTED,
borderDash: [8, 5],
borderWidth: 2,
pointRadius: 0,
fill: false,
tension: 0,
},
{
label: "95% confidence interval",
data: [...studies.map((s) => [s.ciLower, s.ciUpper]), [pooled.ciLower, pooled.ciUpper]],
backgroundColor: MUTED,
barThickness: 4,
borderSkipped: false,
},
{
label: "Study OR (marker size ∝ weight)",
type: "scatter",
data: studies.map((s) => ({ x: s.effect, y: s.study })),
pointStyle: "rect",
pointRadius: studies.map((s) => 5 + s.weight * 0.75),
pointHoverRadius: studies.map((s) => 5 + s.weight * 0.75),
backgroundColor: t.palette[0],
borderWidth: 0,
},
{
label: "Pooled OR",
type: "scatter",
data: [{ x: pooled.effect, y: pooled.study }],
pointStyle: "rectRot",
pointRadius: 20,
pointHoverRadius: 20,
backgroundColor: t.ink,
borderWidth: 0,
},
],
},
options: {
indexAxis: "y",
responsive: true,
maintainAspectRatio: false,
animation: false,
layout: { padding: { top: 10, right: 40, bottom: 10, left: 10 } },
plugins: {
title: { display: true, text: title, color: t.ink, font: { size: 22 } },
subtitle: {
display: true,
text: "Drug A vs. placebo · square markers sized by study weight · diamond = pooled estimate",
color: t.inkSoft,
font: { size: 14, style: "italic" },
padding: { bottom: 12 },
},
legend: {
position: "bottom",
labels: { color: t.ink, font: { size: 14 }, boxHeight: 10, boxWidth: 10 },
},
},
scales: {
x: {
type: "logarithmic",
min: 0.4,
max: 4,
ticks: {
color: t.inkSoft,
font: { size: 14 },
callback: (value) => {
const allowed = [0.4, 0.5, 1, 2, 4];
const rounded = Math.round(value * 100) / 100;
return allowed.includes(rounded) ? rounded : null;
},
},
grid: { color: t.grid },
title: { display: true, text: "Odds Ratio (log scale)", color: t.ink, font: { size: 16 } },
},
y: {
ticks: { color: t.inkSoft, font: { size: 14 } },
grid: { display: false },
},
},
},
});
Runnable source as JSON, for any HTTP client: https://api.anyplot.ai/specs/forest-basic/chartjs/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": "forest-basic",
"language": "javascript",
"library": "chartjs",
"page": "https://anyplot.ai/forest-basic/javascript/chartjs",
"hub": "https://anyplot.ai/forest-basic",
"code_json": "https://api.anyplot.ai/specs/forest-basic/chartjs/code",
"spec_json": "https://api.anyplot.ai/specs/forest-basic",
"render_light_png": "https://storage.googleapis.com/anyplot-images/plots/forest-basic/javascript/chartjs/plot-light.png",
"render_dark_png": "https://storage.googleapis.com/anyplot-images/plots/forest-basic/javascript/chartjs/plot-dark.png",
"interactive_light_html": "https://storage.googleapis.com/anyplot-images/plots/forest-basic/javascript/chartjs/plot-light.html",
"interactive_dark_html": "https://storage.googleapis.com/anyplot-images/plots/forest-basic/javascript/chartjs/plot-dark.html",
"quality_score": 92.0,
"license": "MIT",
"guide": "https://anyplot.ai/llms.txt"
}Part of Meta-Analysis Forest Plot on anyplot.ai.