博学，不错

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Both round() and signif() round numbers to the nearest possibility. So, if the first digit that’s dropped is smaller than 5, the number is rounded down. If it’s bigger than 5, the number is rounded up.

If the first digit that is dropped is exactly 5, R uses a rule that’s common in programming languages: Always round to the nearest even number. round(1.5) and round(2.5) both return 2, for example, and round(-4.5) returns -4.

Contrary to round(), three other functions always round in the same direction:

floor(x) rounds to the nearest integer that’s smaller than x. So floor(123.45) becomes 123 and floor(-123.45) becomes –124.

ceiling(x) rounds to the nearest integer that’s larger than x. This means ceiling (123.45) becomes 124 and ceiling(123.45) becomes –123.

trunc(x) rounds to the nearest integer in the direction of 0. So trunc(123.65) becomes 123 and trunc(-123.65) becomes –123.

Note that for rounding off a 5, the IEC 60559 standard is expected to be used, ‘go to the even digit’. Therefore round(0.5) is 0 and round(-1.5) is -2. However, this is dependent on OS services and on representation error (since e.g. 0.15 is not represented exactly, the rounding rule applies to the represented number and not to the printed number, and so round(0.15, 1) could be either 0.1 or 0.2).

Rounding to a negative number of digits means rounding to a power of ten, so for example round(x, digits = -2) rounds to the nearest hundred.

For signif the recognized values of digits are 1...22, and non-missing values are rounded to the nearest integer in that range. Complex numbers are rounded to retain the specified number of digits in the larger of the components. Each element of the vector is rounded individually, unlike printing.

在哪里用的round函数？