matlab中的sum函数

sum函数用法：

a = sum(x);         %列求和，生成行向量

a = sum(x, 1);      %列求和，生成行向量

a = sum(x, 2);      %行求和，生成列向量

a = sum(x(:));       %矩阵内所有元素求和，生成一个值

>> x = [1,2,3;4,5,6;7,8,9]

x =
     1     2     3
     4     5     6
     7     8     9

>> a = sum(x)

a =
    12    15    18

>> a = sum(x, 1)

a =
    12    15    18

>> a = sum(x, 2)

a =
     6
    15
    24

>> a = sum(x(:))

a =
    45

参考博客：

https://www.baidu.com/link?url=zUUUr9jMKQvjtr9xbw27Hwzx7knGBUh0GdqAqmHzbO1wfmO5fBJSfXePqV7a2ah4tlRYqukZxczAbp_9Fl8apa&wd=&eqid=e6d770a000011cf4000000035af6a2df