# format

##### Encode in a Common Format

Format an R object for pretty printing.

##### Usage

`format(x, …)`# S3 method for default
format(x, trim = FALSE, digits = NULL, nsmall = 0L,
justify = c("left", "right", "centre", "none"),
width = NULL, na.encode = TRUE, scientific = NA,
big.mark = "", big.interval = 3L,
small.mark = "", small.interval = 5L,
decimal.mark = getOption("OutDec"),
zero.print = NULL, drop0trailing = FALSE, …)

# S3 method for data.frame
format(x, …, justify = "none")

# S3 method for factor
format(x, …)

# S3 method for AsIs
format(x, width = 12, …)

##### Arguments

- x
any R object (conceptually); typically numeric.

- trim
logical; if

`FALSE`

, logical, numeric and complex values are right-justified to a common width: if`TRUE`

the leading blanks for justification are suppressed.- digits
how many significant digits are to be used for numeric and complex

`x`

. The default,`NULL`

, uses`getOption("digits")`

. This is a suggestion: enough decimal places will be used so that the smallest (in magnitude) number has this many significant digits, and also to satisfy`nsmall`

. (For the interpretation for complex numbers see`signif`

.)- nsmall
the minimum number of digits to the right of the decimal point in formatting real/complex numbers in non-scientific formats. Allowed values are

`0 <= nsmall <= 20`

.- justify
should a

*character*vector be left-justified (the default), right-justified, centred or left alone. Can be abbreviated.- width
`default`

method: the*minimum*field width or`NULL`

or`0`

for no restriction.`AsIs`

method: the*maximum*field width for non-character objects.`NULL`

corresponds to the default`12`

.- na.encode
logical: should

`NA`

strings be encoded? Note this only applies to elements of character vectors, not to numerical, complex nor logical`NA`

s, which are always encoded as`"NA"`

.- scientific
Either a logical specifying whether elements of a real or complex vector should be encoded in scientific format, or an integer penalty (see

`options("scipen")`

). Missing values correspond to the current default penalty.- …
further arguments passed to or from other methods.

- big.mark, big.interval, small.mark, small.interval, decimal.mark, zero.print, drop0trailing
used for prettying (longish) numerical and complex sequences. Passed to

`prettyNum`

: that help page explains the details.

##### Details

`format`

is a generic function. Apart from the methods described
here there are methods for dates (see `format.Date`

),
date-times (see `format.POSIXct`

) and for other classes such
as `format.octmode`

and `format.dist`

.

`format.data.frame`

formats the data frame column by column,
applying the appropriate method of `format`

for each column.
Methods for columns are often similar to `as.character`

but offer
more control. Matrix and data-frame columns will be converted to
separate columns in the result, and character columns (normally all)
will be given class `"AsIs"`

.

`format.factor`

converts the factor to a character vector and
then calls the default method (and so `justify`

applies).

`format.AsIs`

deals with columns of complicated objects that
have been extracted from a data frame. Character objects and (atomic)
matrices are passed to the default method (and so `width`

does
not apply).
Otherwise it calls `toString`

to convert the object
to character (if a vector or list, element by element) and then
right-justifies the result.

Justification for character vectors (and objects converted to
character vectors by their methods) is done on display width (see
`nchar`

), taking double-width characters and the rendering
of special characters (as escape sequences, including escaping
backslash but not double quote: see `print.default`

) into
account. Thus the width is as displayed by ```
print(quote =
FALSE)
```

and not as displayed by `cat`

. Character strings
are padded with blanks to the display width of the widest. (If
`na.encode = FALSE`

missing character strings are not included in
the width computations and are not encoded.)

Numeric vectors are encoded with the minimum number of decimal places
needed to display all the elements to at least the `digits`

significant digits. However, if all the elements then have trailing
zeroes, the number of decimal places is reduced until
`nsmall`

is reached or at least one
element has a non-zero final digit; see also the argument
documentation for `big.*`

, `small.*`

etc, above. See the
note in `print.default`

about `digits >= 16`

.

Raw vectors are converted to their 2-digit hexadecimal representation
by `as.character`

.

`format.default(x)`

now provides a “minimal” string when
`isS4(x)`

is true.

The internal code respects the option
`getOption("OutDec")`

for the ‘decimal mark’, so if
this is set to something other than `"."`

then it takes precedence
over argument `decimal.mark`

.

##### Value

An object of similar structure to `x`

containing character
representations of the elements of the first argument `x`

in a common format, and in the current locale's encoding.

For character, numeric, complex or factor `x`

, dims and dimnames
are preserved on matrices/arrays and names on vectors: no other
attributes are copied.

If `x`

is a list, the result is a character vector obtained by
applying `format.default(x, …)`

to each element of the list
(after `unlist`

ing elements which are themselves lists),
and then collapsing the result for each element with
`paste(collapse = ", ")`

. The defaults in this case are
`trim = TRUE, justify = "none"`

since one does not usually want
alignment in the collapsed strings.

##### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
*The New S Language*.
Wadsworth & Brooks/Cole.

##### See Also

`format.info`

indicates how an atomic vector would be
formatted.

`formatC`

, `paste`

, `as.character`

,
`sprintf`

, `print`

, `prettyNum`

,
`toString`

, `encodeString`

.

##### Examples

`library(base)`

```
# NOT RUN {
format(1:10)
format(1:10, trim = TRUE)
zz <- data.frame("(row names)"= c("aaaaa", "b"), check.names = FALSE)
format(zz)
format(zz, justify = "left")
## use of nsmall
format(13.7)
format(13.7, nsmall = 3)
format(c(6.0, 13.1), digits = 2)
format(c(6.0, 13.1), digits = 2, nsmall = 1)
## use of scientific
format(2^31-1)
format(2^31-1, scientific = TRUE)
## a list
z <- list(a = letters[1:3], b = (-pi+0i)^((-2:2)/2), c = c(1,10,100,1000),
d = c("a", "longer", "character", "string"),
q = quote( a + b ), e = expression(1+x))
## can you find the "2" small differences?
(f1 <- format(z, digits = 2))
(f2 <- format(z, digits = 2, justify = "left", trim = FALSE))
f1 == f2 ## 2 FALSE, 4 TRUE
## A "minimal" format() for S4 objects without their own format() method:
cc <- methods::getClassDef("standardGeneric")
format(cc) ## "<S4 class ......>"
# }
```

*Documentation reproduced from package base, version 3.6.1, License: Part of R 3.6.1*

### Community examples

**richie@datacamp.com**at Jan 17, 2017 base v3.3.2

By default, `format()` adds leading spaces so that all values have the same length. Setting `trim = TRUE` turns this off. ```{r} x <- 10 ^ (0:4) format(x) format(x, trim = TRUE) ``` `digits` sets the number of significant digits. ```{r} x2 <- c(0, 0.1, 0.12, 0.123, 0.1234) format(x2, digits = 3) ``` Actually, it sets significant digits for the smallest (in magnitude) value, so if you have orders of magnitude range, treat it as a suggestion and fiddle as necessary. ```{r} x <- 10 ^ (0:4) x2 <- c(0, 0.1, 0.12, 0.123, 0.1234) format(x + x2, digits = 3) ``` `digits` can also be useful for examining floating point rounding errors. ```{r} format(sqrt(2) * sqrt(2) - 2, digits = 22) ``` `nsmall` gives the minimum number of decimal places. ```{r} x <- 10 ^ (0:4) x2 <- c(0, 0.1, 0.12, 0.123, 0.1234) format(x + x2, nsmall = 3) ``` You can use `digits` and `nsmall` together; the result has enough digits to satisfy the sig digs and the d.p. criteria. ```{r} x <- 10 ^ (0:4) x2 <- c(0, 0.1, 0.12, 0.123, 0.1234) format(x + x2, digits = 5, nsmall = 1) format(x + x2, digits = 1, nsmall = 5) ``` `justify` lets you enforce left/right/centre justification on character vectors. It has no effect when the input is a number. ```{r} x <- 10 ^ (0:4) format(x, justify = "centre") # does nothing format(format(x, trim = TRUE), justify = "left") format(format(x, trim = TRUE), justify = "centre") ``` `width` pads values with leading spaces to set a minimum output width. ```{r} format(0, width = 10) format(1.2345, width = 1) # width is greater than 1 anyway ``` For objects of class `AsIs`, width sets the maximum output width. ```{r} x <- 10 ^ (0:4) format(I(x), width = 3) ``` Usually `format()` turns `NA` into `"NA"`. Setting `na.encode = FALSE` turns this behaviour off for character vectors. ```{r} format(c("abc", NA), na.encode = FALSE) format(c(1, NA), na.encode = FALSE) # no effect ``` For numeric vectors, you can turn scientific formatting on or off iwth the `scientific` argument. ```{r} format(2 ^ 31 - 1, scientific = FALSE) format(2 ^ 31 - 1, scientific = TRUE) ``` This doesn't work for integers. ```{r} format(.Machine$integer.max, scientific = TRUE) ``` There are more arguments for customising the output for written reports. See [`prettyNum()`](https://www.rdocumentation.org/packages/base/topics/prettyNum) for more. ```{r} format( 123456789.87654321, digits = 17, big.mark = ",", small.mark = " ", small.interval = 2 ) ``` For data frames, the arguments passed to format work on all columns. ```{r} co2 <- CO2[sample(nrow(CO2), 12), ] format(co2, justify = "left", width = 10, scientific = TRUE) ``` Factors default to left justification (in a left-to-right locale?) ```{r} f <- factor(sample(month.name, 25, replace = TRUE)) format(f) format(f, justify = "right", width = 12) ```