1. 清空图表
// 方法:
void clearPlottables(); // 清空所有曲线
void replot(); // 重绘
void deselectAll(); // 取消所有选中
customplot->graph(i)->setSelected(bool); // 选择第i条曲线
// 信号:
void mouseDoubleClick(QMouseEvent *event);
void mousePress(QMouseEvent *event);
void mouseMove(QMouseEvent *event);
void mouseRelease(QMouseEvent *event);
void mouseWheel(QWheelEvent *event);
void plottableClick(QCPAbstractPlottable *plottable,int dataIndex,QMouseEvent *event);
void plottableDoubleClick(QCPAbstractPlottable *plottable,int dataIndex,QMouseEvent *event);
void itemClick(QCPAbstractItem *item,QMouseEvent *event);
void itemDoubleClick(QCPAbstractItem *item,QMouseEvent *event);
void axisClick(QCPAxis *axis,QCPAxis::SelectablePart part,QMouseEvent *event);
void axisDoubleClick(QCPAxis *axis,QCPAxis::SelectablePart part,QMouseEvent *event);
void legendClick(QCPLegend *legend,QCPAbstractLegendItem *item,QMouseEvent *event);
void legendDoubleClick(QCPLegend *legend,QCPAbstractLegendItem *item,QMouseEvent *event);
void selectionChangedByUser(); // 曲线或图例发生选择时 会触发这个信号
void beforeReplot(); // 重绘前
void afterReplot(); // 重绘后