Click the grid to drop a point, drag it to move it. The correlation r and the best-fit line recompute on every pixel. Then load the four classic datasets below: identical averages, identical spread, identical r, identical line — and four pictures that look nothing alike.
click add · drag move · alt+click remove
Keyboard: arrow keys move a crosshair, hold shift for bigger steps. Enter drops a point at the crosshair. Press N or P to step through the existing points; with a point selected the arrow keys move that point. Delete removes it. Escape deselects.
A plain rising trend with ordinary scatter. This is what people picture when they hear “r = 0.82” — and it is only one of the four shapes that produce it.
| set | mean x | mean y | sd x | sd y | r | fit | what it looks like |
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