设置matlab作图数据的个数

有时候用matlab作图时，数据点太多，可以用下面的函数对maker进行设置，这种方法最简单，对数据进行抽样，但是会造成数据的丢失，所以当数据变化缓慢时尚可用，若相邻数据点的值变化较大，则可能导致部分特征失真：

function nummarkers(h,hnum) 
 % NUMMARKERS takes a vector of line handles in h
 % and reduces the number of plot markers on the lines
 % to num. This is useful for closely sampled data.

 % Created: Magnus Sundberg Feb 08, 2001
 % Modified: [email][email protected][/email] May 25, 2013
 lh=length(h);
 lhn=length(hnum);
 if (lhn~=lh && lhn~=1)
 error('The number of markers should be a scalar or a vector with equal length to the number of lines!')
 end
for n = 1:lh
if lhn==1
num=hnum;
elseif lhn==lh
num=hnum(n);
end
if strcmp(get(h(n),'type'),'line')
axes(get(h(n),'parent'));
x = get(h(n),'xdata');
y = get(h(n),'ydata');
lx=length(x);
elseif(lx<2*num)
disp('Warning: Data points are not so many. Not necessary to use this function!')
end
 xd=diff(get(gca,'xlim'));
 yd=diff(get(gca,'ylim'));
 s = [0 cumsum(sqrt(diff(x/xd).^2+diff(y/yd).^2))];
 si = (0:num-1)*s(end)/(num-1);
 ti=zeros(num,1);
 ti(1)=1;
 ti(num)=lx;
for i=2:num-1
[~,ti(i)]=min(abs(s-si(i)));
end
 xi = x(ti);
 yi = y(ti);
 marker = get(h(n),'marker');
 markersize = get(h(n),'markersize');
 color = get(h(n),'color');
 style = get(h(n),'linestyle');
 % make a line with just the markers
 set(line(xi,yi),'marker',marker,'markersize',markersize,'linestyle','none','color',color);
 % make a copy of the old line with no markers
 set(line(x,y),'marker','none','linestyle',style,'color',color);
 % set the x- and ydata of the old line to [], this tricks legend to
%  keep on working
 set(h(n),'xdata',[],'ydata',[]);
 end
 end

 举个例子：

  example:
  t = 0:0.01:pi;
  p = plot(t,sin(t),'-*',t,cos(t),'r-o');
  nummarkers(p,10);
  legend('sin(t)','cos(t)')
 

当maker=10的效果图如下：