当出现Undefined fuction ideal_lp for input arguments of type double .时检查工具箱是否有理想滤波器工具，若有，请检查参数 若没有，请将如上代码转为.m文件并添加。-When an Undefined fuction　ideal_lp　for input the arguments of the type　double . Check the toolkit for ideal filter tool, if yes, please check the parameters　If not, please change the above code into. M file, and add.