SVGPlot::plot

The plot method provides a versatile and fast way of plotting graphs and curves from the svg::plot::SVGPlot class. Generating visualizations is very quick:

	svg::plot::SVGPlot plt;
	plt.plot({1,2,3,4});
	plt.ylabel("some numbers");
	plt.savefig("../docs/svgplot/plot/example1.svg");

generates the following graph:

Example 1

You may be wondering why the x-axis ranges from 0-3 and the y-axis from 1-4. If you provide a single list or array to the plot() method, it is assumed that it represents a sequence of y values, and automatically generates the x values for you, starting from 0 (in this case {0, 1, 2, 3}).

plot() is a versatile method. For example, to plot x versus y, you can do

	svg::plot::SVGPlot plt;
	plt.plot({1, 2, 3, 4}, {1, 4, 9, 16});
	plt.savefig("../docs/svgplot/plot/example2.svg");

to include also specific values on the x axis and therefore generate

Example 2

Of course the plot() method is not limited to bracketed lists. It can also work with any STL linear container of floating point numbers (such as std::list<float>). Additionaly, a python-like arange(<start>,<stop>,<step>) is provided as a list generator. These are illustrated in the following code:

	svg::plot::SVGPlot plt;
	float f=-1.0;
	std::list<float> l; 
	for (int i=0; i<100;++i) l.push_back(f*=-1.005);
	plt.plot(svg::plot::arange(0,5,0.05),l);
	plt.savefig("../docs/svgplot/plot/example3.svg");

that generates

Example 3

Furthermore, it is also possible to use functions as the y parameter. In that case, the function is evaluated for all the real numbers in x and plotted accordingly, as follows:

	svg::plot::SVGPlot plt;
	auto x = svg::plot::linspace(0,5);
	plt.plot(x,[] (float x) { return x*std::sin(x);});
	plt.plot(x,sqrtf);
	plt.savefig("../docs/svgplot/plot/example4.svg");

The above example also illustrates the provided python-like linspace(<start>,<stop>,<nsamples=50>) list generator. It generates the following graph:

Example 4

Formatting

There are several named attributes that can be used for formatting the plot. However, as C++ does not specifically support such feature, these named attributes are implemented as postfix methods, appended consecutively at the end of the plot method call.

These are this named attributes:

markersize(<float>) sets the size of the marker.
marker(<string>) defines the style of the marker represented as a single charater (the same characters as for scatter plots).
markeredgewidth(<float>) sets the width of the line around the markers.
linewidth(<float>) sets the width of the line.
linestyle(<string>) defines the style of the line (- full line, -- dashed line, -. chain line, .. small dashed line). Alternatively, it is also possible to pass a list of floats indicating the size of the lines and spaces among them, consecutively.
color(<color>) defines the color of the plot.
markerfacecolor(<color>) defines the color of the markers.
markeredgecolor(<color>) defined the color of the edges of the markes.

As an usage example for these parameters, we provide this:

	svg::plot::SVGPlot plt;
	plt.plot(svg::plot::arange(0,7,0.5),[] (float x) { return std::sin(x); })
		.linestyle("-.").color(svg::hsv(240,1,1)).linewidth(2)
		.marker("s").markeredgecolor(svg::hsv(240,1,1)).markerfacecolor(svg::yellow).markersize(2.5).markeredgewidth(1);
 	plt.savefig("../docs/svgplot/plot/example5.svg");

which yields the following graph: Example 5

Alternatively, it is possible to use format strings, structured as

"[marker][line][color]"

Each of them is optional. If not provided, a default value (alternating so it actually changes from plot to plout) is used. The exceptions are the interactions between lines and markers: If line is given, but no marker, the data will be a line without markers, and if marker is given but no line, the data will be markers without lines.

Other combinations such as [color][marker][line] are also supported, but note that their parsing may be ambiguous.

The fmt can be either a named attribute or also a nameless attribute added at the end of the data, as illustrated in the following example:

	svg::plot::SVGPlot plt;
	plt.plot(svg::plot::arange(0,20,0.05),
		[] (float x) { return x*std::sin(x);}).fmt("g-");
	plt.plot(svg::plot::arange(0,20,0.05),
		[] (float x) { return x*std::sin(x+0.4*M_PI);}).fmt("r--");
	plt.plot(svg::plot::arange(0,20,0.05),
		[] (float x) { return x*std::sin(x+0.8*M_PI);}).fmt("b-.");
	plt.plot(svg::plot::arange(0,20,0.05),
		[] (float x) { return x*std::sin(x+1.2*M_PI);}).fmt("y:");
	plt.plot(svg::plot::arange(0,20,0.05),
		[] (float x) { return x*std::sin(x+1.6*M_PI);}).fmt("k");
	
	plt.plot(svg::plot::arange(0,20,0.25),
		[] (float x) { return 50+x*std::sin(x);},"go");
	plt.plot(svg::plot::arange(0,20,0.25),
		[] (float x) { return 50+x*std::sin(x+0.4*M_PI);},"r^");
	plt.plot(svg::plot::arange(0,20,0.25),
		[] (float x) { return 50+x*std::sin(x+0.8*M_PI);},"bs");
	plt.plot(svg::plot::arange(0,20,0.25),
		[] (float x) { return 50+x*std::sin(x+1.2*M_PI);},"y+");
	plt.plot(svg::plot::arange(0,20,0.25),
		[] (float x) { return 50+x*std::sin(x+1.6*M_PI);},"k.");
	
	plt.savefig("../docs/svgplot/plot/example6.svg");

which gives the following output: Example 6