Scatter Plot Maker

A scatter plot shows how two measurements move together — hours of study and exam score, temperature and ice-cream sales, height and weight. Paste your x, y pairs (and an optional group column), and this maker draws a clean scatter plot with a least-squares trend line, its equation, the correlation r and R². Logarithmic axes help when values span several powers of ten. Everything is drawn in your browser; download the chart as a PNG or an editable SVG.

How to use this tool

1. Enter one x, y pair per line, or paste two or three columns from a spreadsheet (a header row is fine).
2. Add a title and axis titles — the headers are used if you leave them empty.
3. Choose one trend line for all points, one per group or none, and whether to print the equation and R².
4. Switch on logarithmic axes if needed, set the size and download the PNG or SVG.

Formula

slope b = Σ(x − x̄)(y − ȳ) ÷ Σ(x − x̄)²; intercept a = ȳ − b·x̄; r = Σ(x − x̄)(y − ȳ) ÷ √(Σ(x − x̄)² · Σ(y − ȳ)²)

This is ordinary least squares: the line y = a + b·x that makes the sum of squared vertical distances to the points as small as possible. r runs from −1 (a perfect falling line) through 0 (no straight-line relationship) to +1 (a perfect rising line); R² = r² is the share of the variation in y that the line explains. Correlation is not causation.

Example

For the points (1, 1), (2, 3) and (3, 2), the means are x̄ = 2 and ȳ = 2. Σ(x − x̄)(y − ȳ) = 1 and Σ(x − x̄)² = 2, so the slope is 0.5 and the intercept 2 − 0.5 × 2 = 1: y = 0.5x + 1. With Σ(y − ȳ)² = 2, r = 1 ÷ √(2 × 2) = 0.5 and R² = 0.25.