# skip: vector

## skip()

`skip (expr, skipi, skipj)`

Sets alternating values of `expr` to the missing data value.

`expr     `

A valid grid expression that may have 1 or 2 varying dimensions

`skipi    `

Skip factor in the I dimension of

`expr`
`skipj    `

Skip factor in the J dimension of

`expr`

### Usage Notes

1. This function is often used while displaying wind `arrows` or `barbs` to thin the number of arrows or barbs. It is not necessary to use the `skip` function on both the U and V wind components; it is sufficient to populate only one component with missing data values to suppress the plotting of the wind `arrow` or `barb`.

### Examples

1. Suppose you have a time series of 3-hourly data, but you want to display values at 6-hourly time steps:

```set x 1 set y 1 set t 1 last d skip(var,2)```

2. To display every other grid point in both the X and Y direction:

`d skip(u,2,2);v`

3. To display every grid point in the Y direction, but every 5th grid point in the X direction:

`d skip(u,5,1);v`

4. This example script “d_uv.gs” written by Wesley Ebisuzaki automatically sets the skip factor based on the plot dimensions.
```*
* This function does a d skip(ugrd,n);v
* where n is automatically set to an appropriate value
*
* usage: d_uv ugrd vgrd
*
* v1.1 w. ebisuzaki
* v1.2 4/6/98 revised empirical formula for skip
*
function duv(arg)
u = subwrd(arg,1)
v = subwrd(arg,2)

* get lat/lon info
'query dims'
lons = sublin(result,2)
lats = sublin(result,3)
dx = subwrd(lons,13) - subwrd(lons,11)
dy = subwrd(lats,13) - subwrd(lats,11)

* Determine skip factor
dn = dx
if (dy > dx) ; dn = dy ; endif
skip = dn / 50 + 0.5
if (skip < 1) ; skip=1 ; endif

* Display the plot
'd skip('u','skip');'v```