set(gca,'XTick',1:1:length(x));
set(gca,'XTickLabel',{'15','20','25','30','35','40','45','50','55','60','65','70','75','80','85','90'...
,'95','100','105','110','115','120','125','130','135','140','145','150'...,
'155','160','165','170','175','180','185','190','195','200'});
如上图，左侧区域有空白，我设置XTick和XTiclLabel还是不行，后来xlim(15,200),提示参数不够，那么xlim([15 200])就可以了;
