rockchalk (version 1.4)

plotSeq: Create sequences for plotting

Description

plotSeq is a convenience for the creation of sequence that can be used for plotting example values and calculating predicted values. By default, the length of the plotting sequence will be equal to the length of the original sequence. In that case, the only effect is to create an evenly-spaced set of values. If length.out is specified, the user determines the number of elements in plotSeq.

Usage

plotSeq(x, length.out = length(x))

Arguments

x

an R vector variable

length.out

the number of elements in the desired plotting sequence.

Details

The primary intended usage is for the creation of plotting sequences of numeric variables. It takes a variable's range and the fills in evenly spaced steps. If x is a factor variable, the levels will be returned. Uses of this functionality are planned in the future.

Examples

#Create a quadratic regression

stde <- 14
x <- rnorm(100, m=50, s=10)
y <- 0.2 - 02*x + 0.2*x^2 + stde*rnorm(100)
mod1 <- lm (y ~ poly(x, 2))

plot(x, y, main="The Quadratic Regression")
seqx <- plotSeq(x, length.out=10)
seqy <- predict(mod1, newdata=data.frame(x=seqx))
lines(seqx, seqy, col="red")

# Notice the bad result when a plotting sequence is
# not used.
plot(x, y, main="Bad Plot Result")
seqy <- predict(mod1)
lines(x, seqy, col="green")