%您要的是这种效果?% if(0% if(0.5<=x<1);y=-1;% else,y=0;x=linspace(-5,5,1000);y=zeros(1,length(x));y=x-floor(x);y(find(y<=0 & y>=1))=0;y(find(y>=0.5 & y<1))=-1;y(find(y>0 & y<.5))=1;plot(x,y),hold on;y=0;plot(x,y);axis([-5 5 -2 2])