Function differenceFromLast

Returns a function which yields difference compared to last value.

If no initial value is provided, the first difference will be returned as 0.

Difference can be returned in various formats:

• 'absolute': numerical difference, without sign
• 'numerical': numerical difference, with sign, so you can see if difference is higher or lower
• 'relative': difference divided by last value, giving a proportional difference. Unsigned.
• 'relativeSigned': as above, but with sign

let d = differenceFromLast(`absolute`);
d(10); // 0
d(11); // 1
d(10); // 1
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let d = differenceFromLast(`numerical`);
d(10); // 0
d(11); // 1
d(10); // -1
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let d = differenceFromLast(`relative`);
d(10); // 0
d(11); // 0.1
d(10); // 0.1
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let d = differenceFromLast(`relativeSigned`);
d(10); // 0
d(11); // 0.1
d(10); // -0.1
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An initial value can be provided, eg:

let d = differenceFromLast(`absolute`, 10);
d(11); // 1
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