Presentation on data visualization with plot() function in R

1. DATA VISUALIZATION WITH R:
FUNCTION PLOT()
Vladimir E. Bakhrushin,
Professor, D. Sc.
Vladimir.Bakhrushin@gmail.com

2. Function plot()
Function plot() is the main tool for 2D plotting in R.
If we have two vectors x, y of equal length, function plot(x,y)
allows us to get the graph of y(x) dependence.
If only one variable is given, we will get a graph for which set
vector provide the ordinate values and the points ordinal
numbers are abscissas.

3. Function plot()

4. Some arguments of the plot()
function
Function
plot()
pch
type
main
Vectors x, y
legend
cex
col
lty

5. Combining plots
There is an opportunity to combine several plots into one
overall graph using commands:
old.par <- par(mfrow=c(n,m))
…
par(old.par)
First command places in the window n×m plots (m
horizontally and n vertically).
The last command restores the default graphical parameters.
Between them we have to specify what charts must be built.

6. Graph types
Argument type give us an opportunity to change the view of
graph. It can take the following text values:
"p" – points (default option);
"l" – lines;
"b" – lines between points;
"c" - lines part alone of "b";
"o" – points over lines;
"h" – histogram;
"s", " S" – step curves ;
"n" – no points and lines.

7. Arguments of the plot() function
xlab and ylab – assignment of titles to the coordinate axes,
for example: xlab = "Year", ylab = "Gross domestic product"
xlim and ylim – setting the ranges of values displayed on the​​
abscissa and ordinate axes, respectively; default values of these
arguments are NULL
axes and ann – control of displaying axes and their names;
their values may be "TRUE" or "FALSE"
log – graph in logarithmic or semilogarithmic scale; it may
take values "x", "y" or "xy".

8. Graph types

9. Graph types

10. Titles and subtitles
Argument main is used for creating graph title. Graph subtitle
may be created with argument sub.

11. Titles and subtitles

12. Point character
To set point character we can use argument pch.
First way is to assign a numerical value to argument pch. It
may be taken from the interval 1 – 25 or 32 – 255.
Numbers from 32 to 127 correspond
to ASCII symbols, for example: 33 – !,
34 – ", 35 – # etc. Numbers from 128 to
255 give an opportunity to use some
other symbols, such as Cyrillic alphabet
letters, gothic and so on.

13. Point characters
Another way of setting point characters is combining of
arguments pch and font. The last defines a font of characters.
Default option is font = 1. For the most of other font values we
obtain different variants of writing the same symbols as in the
absence of this argument. For example, at font = 2 bold
characters are used, at font = 3 – italic, at font = 4 – bold italic
etc.
Also we can specify character type directly, for example: pch
= "&".

14. font = 5

15. Colors
To set the color of characters and some other elements we
can use argument col. Also in R there is a possibility to set colors
of individual chart elements. For example, col.main sets the title
color, col.lab – names of axes, col.axes – axes annotations etc.).
Here are the main ways to set colors:
 by name we can set 675 standard colors, for example: col
= "red"; all color names may be obtained with command
colors();
 by numeric code, for example: col = 3 (green);
 by RGB spectrum components, for example: col =
"#FF6347" (tomato).

16. Colors

17. Lines
For setting line type argument lty is used. There are 6
predetermined line types.
If it is necessary you can create your own line types. In this
case, the value of the argument lty is the text sequence of four
numbers from 1 to 9, for example: lty = "4241". This line consists
of the pattern, which includes two dashes of four units in length
and spaces which lengths are alternately equal to two or one
unit.
Line width may be set with argument lwd.

18. Line types

19. Line types

20. Line types

21. Lines ends and joining
Argument lend is used for setting the form of line ends.
It may take such values:
 0 (default) – rounded ends;
 1 – lines ends are straight and perpendicular to lines;
 2 – lines ends are straight and parallel to the coordinate
axes.
Form of lines joining is set with the argument ljoin. It may
take such values:
 0 (за замовченням) – rounded joining;
 1 – sharp-cornered joining;
 2 – truncated joining.

22. Lines ends and joining
Note that the need to hide the names of the axes in the
second graph is enough to specify only when setting the first
line.

23. Lines ends

24. Lines joining

25. Legend
To create the legend function legend() may be used.
Its arguments are: coordinates x and y of the legend
window, vector of the individual lines names, vectors indicated
colors, point characters, line types etc which correspond to
these lines. Argument bty indicates that it is necessary to create
a frame around the legend (value "y"), or that a frame should
not be created (value "n").

26. Legend

27. Література
1.An Introduction to R
2.Kelly Black. R Tutorial
3.Tutorial: Using plot() function
4.R Documentation: Generic X-Y Plotting
5.SPLUS/R Library: Notes From Roger's Seminars on R.
Graphing in R