MATLAB中legend总是出错，即使如下面的小程序都出错，请大神们帮忙解决一下，万分感谢。
小程序如下
x = -pi:pi/20:pi;
plot(x,cos(x),'-ro',x,sin(x),'-.b')
h = legend('cos_x','sin_x',2);
出错问题是
Attempt to call constructor text with incorrect letter case.
Error in scribe.legend/methods>strsize (line 979)
t=text('Parent',ax,...
Error in scribe.legend/methods>getsizeinfo (line 632)
strsizes(k,:) = strsize(h,ppos,fname,fsize,fangl,fwght,interp,str);
Error in scribe.legend/methods (line 19)
[varargout{1:nargout}] = feval(args{:});
Error in scribe.legend/methods>create_legend_items (line 1426)
s = methods(h,'getsizeinfo');
Error in scribe.legend/methods (line 17)
feval(args{:});
Error in scribe.legend (line 115)
methods(h,'create_legend_items',children);
Error in legend>make_legend (line 377)
lh=scribe.legend(ha,orient,location,position,children,listen,strings,propargs{:});
Error in legend (line 280)
[h,msg] = make_legend(ha,varargin(arg:end));
图像能显示，但是就是不显示图例。如果不加图例能正常运行，就是加了图例不行。
x = -pi:pi/20:pi;
plot(x,cos(x),'-ro',x,sin(x),'-.b')
h = legend('cos x','sin x','Location','NW');追问
大神，你能在帮我看看这个么，图例还是显示不出来
one_H_H_1=xlsread('p1_H_H_scan1.xls');
one_H_H_1=sortrows(one_H_H_1,1);
figure(1);
plot(one_H_H_1(:,1),one_H_H_1(:,2),'r-')
a=legend('the polarization of vertical direction',-1);
