斜率交易，顾名思义。抓趋势
X1:C; X2:REF(X1,10); 线斜率:((X1-X2)/X2*100)*10; 斜率20日值:MA(线斜率,10); DRAWTEXT(CROSS(线斜率,斜率20日值),线斜率,'始'); DRAWTEXT(CROSS(斜率20日值,线斜率),斜率20日值,'终');
