matlab 二维数组里放两个坐标什么意思

Question

trace_coo=[tracebackNode.xCoord,tracebackNode.yCoord];
while tracebackNode.parentNode~=0
dis_yuan=dis_yuan+norm([tracebackNode.xCoord-nodeArray(tracebackNode.parentNode).xCoord,tracebackNode.yCoord-nodeArray(tracebackNode.parentNode).yCoord]);
tracebackNode =nodeArray(tracebackNode.parentNode);
trace_coo=[[tracebackNode.xCoord,tracebackNode.yCoord];trace_coo];%???？？？？？？？？？？？？
end

请问上边有问号的那里 ，是什麽意思