The Axis That Straightens Exponentials

You'll learnto read a semi-log plot as the field test for exponential growth.

Ten data points climb from 5 to 5,120 and the first half of them flatline into the floor of the chart. Then the y-axis takes the log treatment — and the same points snap into a perfect straight line. The semi-log plot is the field test for exponential growth, and its slope and intercept hand you the model. The trap is reading that line as linear data. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · log₁₀ y = log₁₀ a + x·log₁₀ b · v4

log the y-axis · straight means exponential

Before you start

What you're looking at

Ten doubling data points, and a vertical axis marked 10, 100, 1000 at equal spacing.

The question

On this axis, does equal visual distance mean adding or multiplying?

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