Q - scatterplot, plot function & trellis linear regressions???

I presume you mean car::scatterplot

A1) plot is a generic function for plotting 'things' and scatterplot
is a specific tool provided by that library

A2) from the documentation one infers that
      1) the straight line is a regression line
      2) the other lines are produced using loess
           a) the solid line is fitted to the data
           b) the dotted lines are created by: "a smoother is applied
to the root-mean-square positive and negative residuals from the loess
line to display conditional spread and asymmetry"

A3) you forgot the data argument (at least).

Cheers,
Simon

Hi R-listers,

Q1) What is the difference between the scatterplot and plot function?

Q2) I am able to make a graph with the scatterplot function:

scatterplot(DevelopIndex ~ Veg,
+ ? ? ? ? ? ? data = Turtle,
+ ? ? ? ? ? ? xlab = "Vegetation border (m)",
+ ? ? ? ? ? ? ylab = "Embryonic development index")

And have been successful. But I do not know if the lines are for: linear,
non-linear, mean, upper and lower limits or percentile? This shows side
boxplots and 4 lines.

Yet this plot only has one regression line and no side boxplots?:

EDIHTL <- lm(DevelopIndex~ HTL, data=Turtle)

plot(DevelopIndex~HTL, data=Turtle, pch=16,

? ? ? xlab="High tide line (m)", ylab="Embryonic development index")

abline(EDIHTL)

Q-3
I am trying to make a trellis of linear regressions. I want 3 windows
displaying 3 events of linear regression (two-way interactions). I have been
trying this:

require(lattice)

library(lattice)
trellis.par.set(col.whitebg())
scatterplot(DevelopIndex~Veg|Aeventexhumed,

+ ? ? ? ? ? ? xlab = "Vegetation border",
+ ? ? ? ? ? ? ylab = "Embryonic development index")
Error in eval(expr, envir, enclos) : object 'DevelopIndex' not found

?Please advise, many thanks.
Jean

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Thank you Simon, 
Yes this was in the library(car). There were no negative values in the
scatterplot graph or negative limits displayed.

Q-2 Are you sure the lines from the scatterplot are not this?:
solid green line: linear regression
solid red line: non-linear regression
upper dashed red line: upper limits 75 percentile
lower dashed red line: lower limits 25 percentile

Q-3 
I am trying to make a trellis of linear regressions but unsuccessful . I
want 3 windows displaying 3 events of linear regression (two-way
interactions). I have been trying this: 

require(lattice)

library(lattice) 
trellis.par.set(col.whitebg()) 
scatterplot(DevelopIndex~Veg|Aeventexhumed, 

+             xlab = "Distance to vegetation border", 
+             ylab = "Embryonic development index") 
Error in eval(expr, envir, enclos) : object 'DevelopIndex' not found 

This error appears and I am not able to produce the trellis of 3 windows
displaying 3 events of linear regressions. 

Please advise
Thank you, Jean

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HI R-listers, 

Thanks for the replies I am convinced of Q 1 and 2. 

Q 3 -  I am still unsuccessful. Aeventexhumed has three events A, B and C. I
am unable to make 3 windows of scatterplot graphs side by side showing the
difference in regression of each event.  With and without lattice I have
tried, but the only graph that is produced is one graph with all three
events (A, B, and C) plotted in one window (R script below).  I want to show
the 3 Aeventexhumed events separately in 3 plots next to each other in one
window. Previously, I have been able to make this is trellis.par.set with
boxplots.

library(car)
library(lattice)
trellis.par.set(col.whitebg())
par(mfrow=c(1,3))
scatterplot(HSuccess~Veg|Aeventexhumed,

+             data = data.to.analyze,
+             xlab ="Distance to vegetation border",
+             ylab = "Hatching success (%)")

Please advise, Jean

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