stepfun
Compute a Step Function

### Description

Computes a left- or right-continuous step function.

### Usage

    stepfun(x, y, f = as.numeric(right), ties = "ordered", right = FALSE)
    is.stepfun(x)
    knots(Fn, ...)
    ## S3 method for class 'stepfun':
    knots(Fn, ...)
    ## S3 method for class 'stepfun':
    summary(object, ...)
    as.stepfun(x, ...)
    ## Default S3 method:
    as.stepfun(x, ...)

### Arguments

x | For stepfun, a numeric vector giving the breakpoints (knots) of the step function. x must be sorted by increasing order and have at least one element. indicates points of plateau levels. For as.stepfun and is.stepfun, x is any object. For print.stepfun, x is an object that inherits from "stepfun".
y | a numeric vector, with length 1 + length(x), indicating the possible values of the step function. If right is FALSE the value at x[i] will be y[i+1], if TRUE it will be y[i].
f | A number between 0 and 1 indicating how the levels of the plateaus between jump points should be calculated. For a plateau between jump points level will be 1-f times the value at the left jump point plus f times the value at the right jump point. The plateau to the left of x[1] will have value y[1], that to the left of x[length(x)] will have value y[length(x)+1], regardless of the value of f or right.
ties | arguments to be passed to function "approxfun".
right | a logical value, if TRUE, the value at x[i] will be y[i], otherwise y[i+1].
Fn | an object inheriting from "stepfun".
digit | the maximum number of digits after the decimal point to print.
... | additional arguments to be passed to or from future functions.

Value

stepfun | returns a function of one argument v, which performs the interpolation specified.
is.stepfun | returns TRUE if x is a function and inherits from "stepfun".
knots | returns a vector containing knots (breakpoints) of a stepfun object.
print.stepfun | returns x, with the invisible set to prevent reprinting.
summary.stepfun | invisibly returns NULL.
as.stepfun | returns a stepfun object implied by its input. This is a generic function and the basic methods do nothing useful: the default method gives an error and the stepfun method returns its input.

See Also
approxfun, print.
Examples

    y0 <- c(1, 2, 3)
    sfun0  <- stepfun(c(4, 5), c(11, 12, 17), f = 0)
    sfun0(c(3.7, 4, 4.2, 5, 5.1))
    is.stepfun(sfun0)
    knots(sfun0)
    print(sfun0)

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