print: Print Values

Description

print prints its argument and returns it invisibly (via invisible(x)). It is a generic function which means that new printing methods can be easily added for new classes.

Usage

print(x, ...)
"print"(x, quote = FALSE, max.levels = NULL, width = getOption("width"), ...)
"print"(x, digits = getOption("digits"), quote = FALSE, na.print = "", zero.print = "0", justify = "none", ...)
"print"(x, useSource = TRUE, ...)

Arguments

an object used to select a method.

...

further arguments passed to or from other methods.

quote

logical, indicating whether or not strings should be printed with surrounding quotes.

max.levels

integer, indicating how many levels should be printed for a factor; if 0, no extra "Levels" line will be printed. The default, NULL, entails choosing max.levels such that the levels print on one line of width width.

width

only used when max.levels is NULL, see above.

digits

minimal number of significant digits, see print.default.

na.print

character string (or NULL) indicating NA values in printed output, see print.default.

zero.print

character specifying how zeros (0) should be printed; for sparse tables, using "." can produce more readable results, similar to printing sparse matrices in \href{https://CRAN.R-project.org/package=#1}{\pkg{#1}}MatrixMatrix.

justify

character indicating if strings should left- or right-justified or left alone, passed to format.

useSource

logical indicating if internally stored source should be used for printing when present, e.g., if options(keep.source = TRUE) has been in use.

Details

The default method, print.default has its own help page. Use methods("print") to get all the methods for the print generic.

print.factor allows some customization and is used for printing ordered factors as well.

print.table for printing tables allows other customization. As of R 3.0.0, it only prints a description in case of a table with 0-extents (this can happen if a classifier has no valid data).

See noquote as an example of a class whose main purpose is a specific print method.

References

Chambers, J. M. and Hastie, T. J. (1992) Statistical Models in S. Wadsworth & Brooks/Cole.

Examples

Run this code

require(stats)

ts(1:20)  #-- print is the "Default function" --> print.ts(.) is called
for(i in 1:3) print(1:i)

## Printing of factors
attenu$station ## 117 levels -> 'max.levels' depending on width

## ordered factors: levels  "l1 < l2 < .."
esoph$agegp[1:12]
esoph$alcgp[1:12]

## Printing of sparse (contingency) tables
set.seed(521)
t1 <- round(abs(rt(200, df = 1.8)))
t2 <- round(abs(rt(200, df = 1.4)))
table(t1, t2) # simple
print(table(t1, t2), zero.print = ".") # nicer to read

## same for non-integer "table":
T <- table(t2,t1)
T <- T * (1+round(rlnorm(length(T)))/4)
print(T, zero.print = ".") # quite nicer,
print.table(T[,2:8] * 1e9, digits=3, zero.print = ".")
## still slightly inferior to  Matrix::Matrix(T)  for larger T

## Corner cases with empty extents:
table(1, NA) # < table of extent 1 x 0 >

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