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Equation 3 · Part 2 · Cities Are Organisms That Refuse to Die: Urban Evolution to 2100

Symbol N

Y(N)=Y0 NβY(N) = Y_0 \, N^{\beta}
NN

What this part means

N is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

Its job in the formula

N is an argument of the function-like quantity on the left; its role is set by that function’s stated inputs.

The passage around this formula

…infrastructure scale sublinearly: length of electrical cable 0.87, road surface 0.83, gasoline stations 0.77, gasoline sales 0.79 [ 1 ] . In the compact notation the paper made famous, a quantity Y relates to population N as Y(N)=Y0 NβY(N) = Y_0 \, N^{\beta}. where β\beta ≈\approx 1.15 for the socioeconomic quantities and β\beta ≈\approx 0.85 for the infrastructural ones. A city twice the size of another does not simply have twice the patents and twice the roads; it tends to have somewhat more than twice the patents and somewhat…

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A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the surrounding passage

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