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### 19.4 Sums and Products

— Built-in Function: sum (x, dim)

Sum of elements along dimension dim. If dim is omitted, it defaults to 1 (column-wise sum).

As a special case, if x is a vector and dim is omitted, return the sum of the elements.

— Built-in Function: prod (x, dim)

Product of elements along dimension dim. If dim is omitted, it defaults to 1 (column-wise products).

As a special case, if x is a vector and dim is omitted, return the product of the elements.

— Built-in Function: cumsum (x, dim)

Cumulative sum of elements along dimension dim. If dim is omitted, it defaults to 1 (column-wise cumulative sums).

As a special case, if x is a vector and dim is omitted, return the cumulative sum of the elements as a vector with the same orientation as x.

— Built-in Function: cumprod (x, dim)

Cumulative product of elements along dimension dim. If dim is omitted, it defaults to 1 (column-wise cumulative products).

As a special case, if x is a vector and dim is omitted, return the cumulative product of the elements as a vector with the same orientation as x.

— Built-in Function: sumsq (x, dim)

Sum of squares of elements along dimension dim. If dim is omitted, it defaults to 1 (column-wise sum of squares).

As a special case, if x is a vector and dim is omitted, return the sum of squares of the elements.

This function is conceptually equivalent to computing

```          sum (x .* conj (x), dim)
```

but it uses less memory and avoids calling conj if x is real.