By default, ChartDirector positions sectors starting from the upward pointing position, and in clockwise direction.
The start angle and layout direction can be changed using
PieChart.setStartAngle.
One common application for the
PieChart.setStartAngle method is to facilitate layout of pie charts containing many small sectors. Please refer to
Pie with Small Sectors.
[The following project is available in "cppdemo/anglepie".]
#include "chartdir.h"
#include
void createChart(int img, const char *filename)
{
char buffer[256];
//query string to determine the starting angle and direction
int angle = 0;
bool clockwise = true;
if (img != 0) {
angle = 90;
clockwise = false;
}
//The data for the pie chart
double data[] = {25, 18, 15, 12, 8, 30, 35};
//The labels for the pie chart
const char *labels[] = {"Labor", "Licenses", "Taxes", "Legal", "Insurance",
"Facilities", "Production"};
//Create a PieChart object of size 280 x 240 pixels
PieChart *c = new PieChart(280, 240);
//Set the center of the pie at (140, 130) and the radius to 80 pixels
c->setPieSize(140, 130, 80);
//Add a title to the pie to show the start angle and direction
if (clockwise) {
sprintf(buffer, "Start Angle = %d degrees\nDirection = Clockwise", angle
);
c->addTitle(buffer);
} else {
sprintf(buffer, "Start Angle = %d degrees\nDirection = AntiClockwise",
angle);
c->addTitle(buffer);
}
//Set the pie start angle and direction
c->setStartAngle(angle, clockwise);
//Draw the pie in 3D
c->set3D();
//Set the pie data and the pie labels
c->setData(DoubleArray(data, sizeof(data)/sizeof(*data)), StringArray(
labels, sizeof(labels)/sizeof(*labels)));
//Explode the 1st sector (index = 0)
c->setExplode(0);
//output the chart
c->makeChart(filename);
//free up resources
delete c;
}
int main(int argc, char *argv[]) {
createChart(0, "anglepie0.png");
createChart(1, "anglepie1.png");
return 0;
}
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