怎样直接在内存中计算并赋值给变量？

[#1]

例如: 身高体重同时符合条件的个数

谢谢！

[#2]

dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
s = Sum( dt[0, "height"] < 60 :* dt[0, "weight"] < 90 );

//s=5

？？

[#3]

I SEE

dt = Open( "$SAMPLE_DATA/Big Class.jmp" );
s = Sum( dt[0, "height"] < 60 :* (dt[0, "weight"] < 90) );