用matlab求下面两个算式卷积 x(n)=2^n(0<=t<=1);h(n)=(1/2)^n(0<=t<=3);

function [y,ny]=conv_m(x,nx,h,nh)

t1=[0:0.1:1];
f1=2.^t1;
t2=[0:0.1:3];
f2=(1/2).^t2;
[y,ny]=conv_m(f1,t1,f2,t2);
subplot(3,1,1);stem(t1,f1)
subplot(3,1,2);stem(t2,f2)
subplot(3,1,3);stem(ny,y)
哪位大神速速指点，哪里有错误啊