Customizing Graphics with Base R: A Comprehensive Guide

1. Customizing Graphs Base graphics options

2. plot() • The workhorse plotting function • plot(x) plots values of x in sequence or a barplot • plot(x, y) produces a scatterplot • plot(y~x, data=data.frame) produces a scatterplot • Many statistical functions produce results that can be plotted using plot

3. Variations on plot() • type = “p”, “l”, “b”, or “n” for points, lines, both, or no plot (also “c”, “o”, “h”, “s”, “S”) • asp = sets the y/x aspect ratio (asp=1 for mapping) • Full control over labels, axes, symbols, lines, etc

4. Parameter cex= • cex controls the size of text and symbols in a graph • cex = 1 is the default size (except for main= where it is 2) • cex.main, cex.sub, cex.lab, cex.axis control specific parts of the plot • cex = alone usually controls the size of pch, the plot character

5. Symbol/Line Styles • pch = (plot character) specifies the symbol set • cex = symbol size • lty = specifies the line type • lwd = specifies the line thickness

9. Parameter col= • col = controls the color of a symbol or line • col.axis, col.lab, col.main, col.sub control colors of other parts of the graph • bg = background color • col takes a name or hexadecimal color value

10. Color • colors() for list of 657 named colors • palette() gives the default list of eight colors • gray() gives grayscale from black - gray(0) to white – gray(1)

13. Color Palettes • rainbow(number) generates a spectrum from red to violet based on hue, saturation, and value (hsv) • rainbow_hcl(number) similar, but using hue, chroma, and luminance color space (hcl) • Help pages for these give several other palettes

20. Fonts • family = sets the font family – “serif”, “sans”, and “mono” – others may be defined by specific graphic devices • font = sets the font, 1 plain, 2 bold, 3 italic, 4 bold italic, 5 symbol • Fonts may be device dependent

22. Labels • main = “This is the title”, cex.main, col.main, font.main • sub = “This is the subtitle”, cex.sub, col.sub, font.sub • Axis labels • lab = “This is the x-axis label” • ylab = “This is the y-axis label” • cex.lab, col.lab, font.lab, las (0, 1, 2, 3)

23. Axes • Default usually selects reasonable axes • xlim, ylim set limits for axes • xaxp, yaxp set tick marks • xlog, ylog to use log scale • xaxt , yaxt “n” suppresses plotting

24. axis() • Use to add a customized axis or position an axis on the top or right of the plot or in the margin of the plot • at = specifies location of tickmarks • labels = specifies labels

25. Adding to a Graph 1 • Plot sets up coordinates • grid – add gridlines • abline – add regression, vertical, or horizontal lines (full plot window) • points – add points • lines – add lines • segment – add line segments

26. Adding to a Graph 2 • text – add text to plot • legend (locator, position, coords) • arrows – draw arrows • rect – draw rectangles • polygon – draw polygons • ellipse – draw probability ellipse • matlines – draw multiple lines

27. Margins • Must be set before calling plot • oldpar <- par() # to save current • par(mar= c(bottom, left, top, right)) if you need more space for labels, titles, etc

28. Multiple Graphs • par(mfrow=c(rows, cols)) plots in rows • Par(mfcol=c(rows, cols)) plots in columns