capture-n-write function

Capture output and Write / Print First and Last Parts

Capture output and print first and last parts, eliding middle parts. Particularly useful for teaching purposes, and, e.g., in Sweave (RweaveLatex).

By default, when middle = NA, capture.output(EXPR, first, last)

basically does

co <- capture.output(EXPR)
    writeLines(head(co, first))
    cat( ... dotdots ...)
    writeLines(tail(co, last))

capture.and.write(EXPR, first, last = 2, middle = NA,
                  i.middle, dotdots = " ....... ", n.dots = 2)

Arguments

• EXPR: the (literal) expression the output of which is to be captured.
• first: integer: how many lines should be printed at beginning.
• last: integer: how many lines should be printed at the end.
• middle: numeric (or NA logical):
• i.middle: index start of middle part
• dotdots: string to be used for elided lines
• n.dots: number of dotdots lines added between parts.

Returns

return value of capture.output(EXPR).

See Also

head, tail

Author(s)

Martin Maechler, ETH Zurich

Examples

x <- seq(0, 10, by = .1)

## for matrix, dataframe, .. first lines include a header line:
capture.and.write( cbind(x, log1p(exp(x))),  first = 5)

## first, *middle* and last :
capture.and.write( cbind(x, x^2, x^3), first = 4, middle = 3, n.dots= 1)