addLines function

Superimpose regression lines on a plotted plane

The examples will demonstrate the intended usage.

addLines(to = NULL, from = NULL, col, lwd = 2, lty = 1)

Arguments

• to: a 3d plot object produced by plotPlane
• from: output from a plotSlopes or plotCurves function (class="rockchalk")
• col: color of plotted lines (default: "red")
• lwd: line width of added lines (default: 2)
• lty: line type of added lines (default: 1)

Returns

NULL, nothing, nicht, nada.

Details

From an educational stand point, the objective is to assist with the student's conceptualization of the two and three dimensional regression relationships.

Examples

##library(rockchalk)

set.seed(12345)

dfadd <- genCorrelatedData2(100, means = c(0,0,0,0), sds = 1, rho = 0,
       beta = c(0.03, 0.01, 0.1, 0.4, -0.1), stde = 2)

dfadd$xcat1 <- gl(2,50, labels=c("M","F"))

dfadd$xcat2 <- cut(rnorm(100), breaks=c(-Inf, 0, 0.4, 0.9, 1, Inf),
                   labels=c("R", "M", "D", "P", "G"))

dfadd$y2 <- 0.03 + 0.1*dfadd$x1 + 0.1*dfadd$x2 +
    0.25*dfadd$x1*dfadd$x2 + 0.4*dfadd$x3 - 0.1*dfadd$x4 +
    0.2 * as.numeric(dfadd$xcat1) +
    contrasts(dfadd$xcat2)[as.numeric(dfadd$xcat2), ] %*% c(-0.1, 0.1, 0.2, 0) +
    1 * rnorm(100)

summarize(dfadd)

## linear ordinary regression
m1 <- lm(y ~ x1 + x2 + x3 + x4, data = dfadd)
summary(m1)

mcDiagnose(m1)

## These will be parallel lines

plotSlopes(m1, plotx = "x1", modx = "x2", modxVals = "std.dev.",
           n = 5, main = "A plotSlopes result with \"std.dev.\" values of modx")

m1ps <- plotSlopes(m1, plotx = "x1", modx = "x2", modxVals = c(-2,0,2))

m1pp <- plotPlane(m1, plotx1 = "x1", plotx2 = "x2",
                  ticktype = "detailed", npp = 10)

addLines(from = m1ps, to = m1pp, lty = 1, lwd = 2)

m1pp <- plotPlane(m1, plotx1 = "x1", plotx2 = "x2", ticktype = "detailed",
                  npp = 10)
addLines(from = m1ps, to = m1pp, lty = 2, lwd = 5, col = "green")

## Other approach would wrap same into the linesFrom argument in plotPlane

plotPlane(m1, plotx1 = "x1", plotx2 = "x2", ticktype = "detailed",
          npp = 10, linesFrom = m1ps)

## Need to think more on whether dotted lines from ps object should
## be converted to solid lines in plotPlane.

Author(s)

Paul E. Johnson pauljohn@ku.edu