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11.113 Sample ‘section’ ¶

Example of section to separate data and join it back.

MGL code:

subplot 1 1 0 '<_':title 'Section&Join sample'
axis:box:line -1 0 1 0 'h:'
# first lets demonstrate 'join'
new aa 11 'x^2':new a1 3 '-x':new a2 15 'x^3'
join aa a1:join aa a2
# add x-coordinate
new xx aa.nx 'x':join aa xx
plot aa(:,1) aa(:,0) '2y'
# now select 1-st (id=0) section between zeros
section b1 aa 0 'x' 0
plot b1(:,1) b1(:,0) 'bo'
# next, select 3-d (id=2) section between zeros
section b3 aa 2 'x' 0
plot b3(:,1) b3(:,0) 'gs'
# finally, select 2-nd (id=-2) section from the end
section b4 aa -2 'x' 0
plot b4(:,1) b4(:,0) 'r#o'

C++ code:

void smgl_section(mglGraph *gr)
{
	gr->SubPlot(1,1,0,"<_");
	if(big!=3)	gr->Title("Section&Join sample");
	gr->Axis();	gr->Box();	gr->Line(mglPoint(-1,0),mglPoint(1,0),"h:");
	// first lets demonstrate 'join'
	mglData aa(11), a1(3), a2(15);
	gr->Fill(aa,"x^2");	gr->Fill(a1,"-x");	gr->Fill(a2,"x^3");
	aa.Join(a1);	aa.Join(a2);
	// add x-coordinate
	mglData xx(aa.nx);	gr->Fill(xx,"x");	aa.Join(xx);
	gr->Plot(aa.SubData(-1,1), aa.SubData(-1,0), "2y");
	// now select 1-st (id=0) section between zeros
	mglData b1(aa.Section(0,'x',0));
	gr->Plot(b1.SubData(-1,1), b1.SubData(-1,0), "bo");
	// next, select 3-d (id=2) section between zeros
	mglData b2(aa.Section(2,'x',0));
	gr->Plot(b2.SubData(-1,1), b2.SubData(-1,0), "gs");
	// finally, select 2-nd (id=-2) section from the end
	mglData b3(aa.Section(-2,'x',0));
	gr->Plot(b3.SubData(-1,1), b3.SubData(-1,0), "r#o");
}