如图可见, 第二次输入只多了末尾的matrixform. 居然影响了Drop操作对行列的判断! 偶是不是火星了~大家给点评论啊~
附上代码给大家实验:
datarecords={{"Joe", "Smith",158,64.4},{"Mary", "Davis",137,64.4},{"Bob", "Lewis",141,62.8},{"John", "Thompson",235,71.1},{"Lewis", "Black",225,71.4},{"Sally", "Jones",168,62.},{"Tom", "Smith",243,70.9},{"Jane", "Doe",225,71.4}};
Drop[datarecords,None,{1,2}]//MatrixForm
datarecords={{"Joe", "Smith",158,64.4},{"Mary", "Davis",137,64.4},{"Bob", "Lewis",141,62.8},{"John", "Thompson",235,71.1},{"Lewis", "Black",225,71.4},{"Sally", "Jones",168,62.},{"Tom", "Smith",243,70.9},{"Jane", "Doe",225,71.4}}//MatrixForm;
Drop[datarecords,None,{1,2}]//MatrixForm

因为//MatrixForm以后就不再是一个列表了，而是成为了一种新的格式，你可以理解为MatrixForm命令把列表变成了一张图片，从此就只能看不能作为列表参与运算了
比如你可以感受一下这个例子