求高手帮助，为什么会出现butter函数的问题，怎么解决？求大侠指点！

Question

写好的程序运行时出现如下错误，
??? Undefined function or method 'butter' for input arguments of type 'double'.
Error in ==> Shot_time_cross_zero_rate at 4
[b,a]=butter(4,[0.025 0.85]);%4阶巴特沃斯滤波器，上下截止频率100Hz，3400Hz

程序前4行如下
clear all
close all
[x,fs,bit]=wavread('F:\test.wav');
[b,a]=butter(4,[0.025 0.85]);%4阶巴特沃斯滤波器，上下截止频率100Hz，3400Hz

Answer 1

从错误提示来看，应该是传递给butter函数的实参错误。从楼主的调用来看应该是下面这三种情况：应该是少了一个参数，导致报错。If Wn is a two-element vector, Wn = [W1 W2], butter returns an&nbsp;order 2N bandpass filter with passband W1 < W < W2.[B,A] = butter(N,Wn,'high') designs a highpass filter.[B,A] = butter(N,Wn,'low') designs a lowpass filter.[B,A] = butter(N,Wn,'stop') is a bandstop filter if Wn = [W1 W2].

Answer 2

两种可能：1;你的matlab版本过低，版本没有butter函数2：你安装的matlab没安装完整，缺少butter函数文件不如重新下载个2012版的重新安装下，鬼知道下次哪个函数不能用了