zapsmall
Coerce Small Numbers to Zero for Printing

### Description

Returns an object like the input, but with numbers that are close to zero and much smaller than the largest values of the input, rounded to zero.

### Usage

    zapsmall(x, digits = getOption("digits"))

### Arguments

x | a numeric vector, a matrix, or an array.
digits | the number of digits to be printed after the decimal point. The default is the value of the digits option.

### Details

The value specified for digits is modified internally to be max(digits - log10(m), 0), where m is max(abs(x[!is.na(x)])). This value is used as the digits argument to the round function. Thus, if x consists solely of very small numbers of approximately equal magnitude, no values are zapped.
The usual use for zapsmall is to massage the results of double-precision arithmetic, so that values that might be expected to be zero actually appear as zero. For example, matrix multiplications that are supposed to yield triangular or diagonal matrices often result in small values in the off-diagonal entries. Using zapsmall can help you confirm that the correct answer is being calculated.
Value
returns an object like x, but with small numbers "zapped" to be exactly zero. If x consists solely of small numbers, it is returned unmodified.
References
Chambers, John M. 1998. Programming with Data. New York, NY: Springer.
See Also
round.
Examples

    c(sin(pi), cos(pi))
    zapsmall(c(sin(pi), cos(pi)))
    e <- exp(1)*10^(-5:1)
    print(e, digits = 4)
    # 2.718e-05 2.718e-04 2.718e-03 2.718e-02 2.718e-01 2.718e+00 2.718e+01
    zapsmall(e, digits = 4)
    # 0.000  0.000  0.003  0.027  0.272  2.718 27.183

Package base version 6.1.5-18
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