请问如何在矩阵求列和时加入条件？
     [,1] [,2] [,3] [,4]  [,5]  [,6]  [,7]  [,8]  [,9] [,10] [,11] [,12] [,13] [,14]
[1,] 0.00 2.22 2.44 2.68  2.95  3.25  3.57  3.93 -1.15  0.00  2.22  2.44  2.68  2.95
[2,] 2.22 2.44 2.68 2.95  3.25  3.57  3.93 -1.15  0.00  2.22  2.44  2.68  2.95  3.25
[3,] 2.44 2.68 2.95 3.25  3.57  3.93 -1.15  0.00  2.22  2.44  2.68  2.95  3.25  3.57
[4,] 2.68 2.95 3.25 3.57  3.93 -1.15  0.00  2.22  2.44  2.68  2.95  3.25  3.57  3.93
[5,] 2.95 3.25 3.57 3.93 -1.15  0.00  2.22  2.44  2.68  2.95  3.25  3.57  3.93 -1.15


colSums求列和时，只将大于等于0的数值求和，忽略负值

谢谢