ctioga2 the polymorphic plotting program

Legends

One important thing with graphs is a legible legend that tells all that needs to be said… ctioga2 provides various ways to do that.

How to specify legends

Legends can either be specified before using the command --legend or as an option to the plot:

ctioga2 -X --math --legend '$\sin x$' 'sin(x)' \
	'cos(x)' /legend '$\cos x$'

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Additional lines of information can be added using the --legend-line command. It can be styled to your taste:

ctioga2 -X --math --legend-line 'Trigonometric' /color Blue \
	--legend '$\sin x$' 'sin(x)' \
	'cos(x)' /legend '$\cos x$' \
	--legend-line 'Non-trigonometric' /color Red \
	'0.1 * x' /legend '$x/10$'

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See how in this case the plot gently expands to leave space for the legend. When that is not desired, it is possible to use the /count-legend option of the --page-size command:

ctioga2 -r 9cmx7cm /count-legend=true \
	-X --math --legend-line 'Trigonometric' /color Blue \
	--legend '$\sin x$' 'sin(x)' \
	'cos(x)' /legend '$\cos x$' \
	--legend-line 'Non-trigonometric' /color Red \
	'0.1 * x' /legend '$x/10$'

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This produces a plot of exactly 9cmx7cm, counting the legend in, while without this option the graph has a fixed size, but the space allocated for the legend expands as necessary.

Legends inside the plot

I don’t like much having the legends on the side, as it tends to leave a lot of white space, though admittedly sometimes there’s no way around it. ctioga2 allows to place the legends inside the plot, using the --legend-inside command:

ctioga2 -X --math \
	--legend-inside tc \
	'x' /legend '$x$' \
	'x**2' /legend '$x^2$' \
	'x**3' /legend '$x^3$' \

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The tc specification requests to place the top center of the legend at the top center of the graph. Placement can be refined by giving an additional coordinate specification:

ctioga2 -X --math \
	--legend-inside lt:0.1,0.82 /scale 1.2 /dy 1.1 \
	'x' /legend '$x$' \
	'x**2' /legend '$x^2$' \
	'x**3' /legend '$x^3$' \

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This lt:0.1,0.82 means: place the top left corner of the legends at the position 0.1,0.82 (counting from the bottom left corner; 1,1 is the top right corner of the plot).

It additionally demonstrates the use of options to --legend-inside that can be used to tweak the look of the legend, such as its size and spacing between consecutive lines. --legend-style takes the same options, but without imposing the placement (which can be useful to tweak the look of the outer legends).

Fancy legend frames

Using the /frame_ options to --legend-inside or to --legend-style, one can draw possibly filled frames around the legend. Using a fill transparency, it is even possible to dim what is underneath (text never gets dimmed this way, though):

math
legend-inside lc /scale 1.2 /dy 1.1 /frame-shape round /frame-padding 3mm \
        /frame-color=Blue /frame-fill-color='Blue!20' \
        /frame-fill-transparency=0.3 /frame-style=Dots
plot 'x' /legend '$x$'
plot 'x**2' /legend '$x^2$'
plot 'x**3' /legend '$x^3$'

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Here, we also demonstrate a frame with rounded corners using the option /frame-shape=round.

Try using a white background too !

Multicolumn legends

With the --legend-multicolumn command, one can lay out parts of the legend in several columns:

math /xrange=-1:1
legend-inside br  /dy 1.1
legend-line 'First powers of $x$'
legend-multicol /columns=2 /dx=4mm
plot 'x' /legend '$x$'
plot 'x**2' /legend '$x^2$'
plot 'x**3' /legend '$x^3$'
plot 'x**4' /legend '$x^4$'
legend-line 'Inside'
plot 'x**5' /legend '$x^5$'
legend-multicol-end
legend-line 'End of multicol'

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Only the legends of objects between the calls to --legend-multicolumn and --legend-multicolumn-end are laid out in several columns. Spacing between the columns can be fine-tuned using the /dx option to --legend-multicolumn.

Fine-tuning of legends

Many aspects of the appearance of the legends can be fine-tuned using options to --legend-style or directly --legend-inside, such as the overall size of the pictogram and the size of the symbol:

math /xrange=-1:1
legend-inside tc  /dy 1.1 /picto-width 3mm /symbol-scale 2 /scale=1.3
plot 'x**2' /legend '$x^2$'
math /samples=20
plot 'x' /legend '$x$' /marker Square

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Separate legend pictograms

Starting from ctioga2 version 0.14, you can draw separate legend pictograms for a given curve using --draw-legend-pictogram, provided you give it a name using the /id option to --plot command:

math
plot 'x' /id x
plot 'x**2/4' /marker=Square /id x2
draw-legend-pictogram 0,12 x
draw-legend-pictogram -3,15 x2

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