stepblock {stepR}

Step function

Description

Constructs an object containing a step function sampled over finitely many values.

Usage

stepblock(value, leftEnd = c(1, rightEnd[-length(rightEnd)] + 1), rightEnd, x0 = 0)
## S3 method for class 'stepblock'
x[i, j, drop = if(missing(i)) TRUE else if(missing(j)) FALSE else length(j) == 1, ...]
## S3 method for class 'stepblock'
print(x, ...)
## S3 method for class 'stepblock'
plot(x, type = "c", xlab = "x", ylab = "y", main = "Step function", sub = NULL, ...)
## S3 method for class 'stepblock'
lines(x, type = "c", ...)

Arguments

value

a numeric vector containing the fitted values for each block; its length gives the number of blocks

leftEnd

a numeric vector of the same length as value containing the left end of each block

rightEnd

a numeric vector of the same length as value containing the right end of each block

x0

a single numeric giving the last unobserved sample point directly before sampling started, i.e. before leftEnd[1]

x

the object

i, j, drop

see [.data.frame

type

"c" to plot jumps in the middle between the end of the previous block (or x0) and the beginning of the following block; "e" to jump at the end of the previous block; "b" to jump at the beginning of the following block; capital letters also plot points

xlab, ylab, main, sub

see plot.default

...

for generic methods only

Value

For stepblock an object of class stepblock, i.e. a data.frame with columns value, leftEnd and rightEnd and attribute x0.

Note

For the purposes of this package step functions are taken to be left-continuous, i.e. the function jumps after the rightEnd of a block.

However, step functions are usually sampled at a discrete set of points so that the exact position of the jump is unknown, except that it has to occur before the next sampling point; this is expressed in the implementation by the specification of a leftEnd within the block so that every rightEnd and leftEnd is a sampling point (or the boundary of the observation window), there is no sampling point between one block's rightEnd and the following block's leftEnd, while the step function is constant at least on the closed interval with boundary leftEnd, rightEnd.

See Also

step, stepfit, family, [.data.frame, plot, lines

Examples

# step function consisting of 3 blocks: 1 on (0, 3]; 2 on (3, 6], 0 on (6, 8]
# sampled on the integers 1:10
f <- stepblock(value = c(1, 2, 0), rightEnd = c(3, 6, 8))
f
# show different plot types
plot(f, type = "C")
lines(f, type = "E", lty = 2, col = "red")
lines(f, type = "B", lty = 3, col = "blue")
legend("bottomleft", legend = c("C", "E", "B"), lty = 1:3, col = c("black", "red", "blue"))