matlab函数，专门计算列车车体横向sperling平稳性指标。调用方式：y=lridex(acc)，其中acc为测得的或仿真得到的车体横向加速度（不包括时间列）。-matlab function, specifically calculate the train body lateral sperling smooth indicators. The invocation: y = lridex (ACC), wherein acc obtained for the measured or simulation vehicle body lateral acceleration (not including the time column).