datana (version 1.1.5)

plotrend: Function for building a scatterplot with a superposing smoothed line

Description

The function creates a scatterplot with a superposing smoothed line as a way to reveal any potential pattern between the variables.

Usage

plotrend(
  x = x,
  y = y,
  col = "black",
  linecol = "red",
  lwd = 2,
  xlab = NULL,
  ylab = NULL,
  ...
)

Value

The function returns the above described graph.

Arguments

x

A numeric vector representing the X-axis variable.

y

A numeric vector representing the Y-axis variable (response).

col

A string specifying the color of the data points. The default is "black".

linecol

A string specifying the smooth line color. The default is set to "red".

lwd

the width of the smooth line to be drawn. The default is set to 2.

xlab

(optional) A string specifying X-axis label.

ylab

(optional) A string specifying Y-axis label.

...

other graphical parameters (see par and section 'Details' below).

Author

Christian Salas-Eljatib

Details

Notice that the smoothed-line is derived from a rather standard algorithm (i.e., loess), implemented in the function smoothfit, thus it is only an approximation.

Commonly used graphical parameters are: col The colors for lines and points. Multiple colors can be specified so that each point can be given its own color. If there are fewer colors than points they are recycled in the standard fashion. Lines will all be plotted in the first colour specified. bg a vector of background colors for open plot symbols, see points. Note: this is not the same setting as par("bg"). pch a vector of plotting characters or symbols: see points. cex a numerical vector giving the amount by which plotting characters and symbols should be scaled relative to the default. This works as a multiple of par("cex"). NULL and NA are equivalent to 1.0. Note that this does not affect annotation: see below. lty a vector of line types, see par. cex.main, col.lab, font.sub, etc settings for main- and sub-title and axis annotation, see title and par. lwd a vector of line widths, see par.

References

• Salas-Eljatib C. 2021. Análisis de datos con el programa estadístico R: una introducción aplicada. Ediciones Universidad Mayor. Santiago, Chile. 170 p. https://eljatib.com

• Salas C, Stage AR, and Robinson AP. 2008. Modeling effects of overstory density and competing vegetation on tree height growth. Forest Science 54(1):107-122. tools:::Rd_expr_doi("10.1093/forestscience/54.1.107")

Examples

df <- datana::maple
head(df)
m1<-lm(leaf~dbh,data=df)
# Example 1, a residual plot
plotrend(x=df$dbh,y=residuals(m1))
abline(h=0)