`sum (`

*expr, dim1, dim2, <,tinc>* <,-b>)

Sums the result of

over the specified dimension range.
If the summing dimension is time, an optional time increment *expr*

may be specified.
*tincr*

*expr*

- any valid GrADS expression *dim1*

- the start point for the sum*dim2*

- the end point for the sum*tinc*

- optional increment for time summing`-b `

- use exact boundaries

and *dim1*

are standard
GrADS dimension expressions whose dimensions must match.
*dim2*

- The limits and intervals of the summing are set according to the grid coordinates
of the default file. If

and*dim1*

are specified in world coordinates, the coordinates are converted to the nearest integer grid coordinates based on the scaling of the default file.*dim2* - The end points are given normal weighting, unless the
`-b`

boundary flag is specified. The boundry flag indicates that the sum should be taken to the exact boundaries specified by

and*dim1*

, rather than the nearest grid points.*dim2* - In the Y dimension, when the boundary is beyond the pole, the
`asum`

function recognizes this and weights appropriately. To calculate an sum without any weighting, use the`sumg`

function.