NCL Home > Documentation > Functions > General applied math

# round

Rounds a float or double variable to the nearest whole number.

## Prototype

```	function round (
x    : float,    ; or double
opt  : integer
)

return_val [dimsizes(x)] :  (see below for type)
```

## Arguments

x

An array of one or more values of any dimensionality.

opt

opt=0: return values of the same type as x
opt=1: return values of type float
opt=2: return values of type double
opt=3: return values of type integer

## Description

This function returns results similar to the Fortran function "anint"; that is, it rounds the input to the nearest whole number. It differs in that it allows the user to specify the type of the return values. Also, missing values are ignored.

## Examples

Example 1

The one caveat to using this function is that user must be aware that if opt=3 is chosen, then the _FillValue may be affected. Note: NCL requires that the _FillValue have the same type as the parent variable.

Example 2

```  x  = 5.7
q  = round(x,0)   ; ===> q=6.0  (type float)
r  = round(x,1)   ; ===> r=6.0  (type float)
d  = round(x,2)   ; ===> d=6.0  (type double)
i  = round(x,3)   ; ===> i=6    (type integer)
```
Example 2

```  x  = (/-5. , -4.7, -4.5, -4.3, -0.8, -0.5, -0.2, -50.6 \
, 5. ,  4.7,  4.5,  4.3,  0.8,  0.5,  0.2,  50.6 \
,-99. /)
x@_FillValue = -99.

q  = round(x,0)   ; ===>  (/-5.,-5.,-5.,-4.,-1.,-1., 0.,-51. \
, 5., 5., 5., 4., 1., 1., 0., 51. \
,-99. /)

f  = round(x,1)   ; ===>  (/-5.,-5.,-5.,-4.,-1.,-1., 0.,-51. \
, 5., 5., 5., 4., 1., 1., 0., 51. \
,-99. /)

d  = round(x,2)   ; ===>  (/-5.,-5.,-5.,-4.,-1.,-1., 0.,-51. \
, 5., 5., 5., 4., 1., 1., 0., 51. \
,-99. /)

i  = round(x,3)   ; ===>  (/-5 ,-5 ,-5 ,-4 ,-1 ,-1 , 0 ,-51 \
, 5 , 5 , 5 , 4 , 1 , 1 , 0 , 51 \
,-99   /)
```
Example 3

Here is an example where the _FillValue will change.

```  x  = (/-5. , -4.7, -4.5, -4.3, -0.8, -0.5, -0.2, -50.6 \
, 5. ,  4.7,  4.5,  4.3,  0.8,  0.5,  0.2,  50.6 \
,-99.9 /)
x@_FillValue = -99.9

i  = round(x,3)   ; ===>  (/-5 ,-5 ,-5 ,-4 ,-1 ,-1 , 0 ,-51 \
, 5 , 5 , 5 , 4 , 1 , 1 , 0 , 51 \
,-100  /)
```
Example 4:

Like example 3, but assume you want a _FillValue equal to -99. There are two approaches:

1. If the user is certain that in the original x array the value -99 is unique, then simply change the _FillValue to -99:
```  x  = (/-5. , -4.7, -4.5, -4.3, -0.8, -0.5, -0.2, -50.6, \
5. ,  4.7,  4.5,  4.3,  0.8,  0.5,  0.2,  50.6, \
-99.9 /)
x@_FillValue = -99.9   ; original _FillValue

x@_FillValue = -99.    ; NCL will change all -99.9 to -99.

i  = round(x,3)   ; ===>  (/-5 ,-5 ,-5 ,-4 ,-1 ,-1 , 0 ,-51, \
5 , 5 , 5 , 4 , 1 , 1 , 0 , 51, \
-99  /)
```
2. If the user is not certain, then some value should be chosen that is unique.
```  x  = (/-5. , -4.7, -4.5, -4.3, -0.8, -0.5, -0.2, -50.6, \
5. ,  4.7,  4.5,  4.3,  0.8,  0.5,  0.2,  50.6, \
-99.9 /)
x@_FillValue = -99.9     ; original _FillValue

x@_FillValue = 1234567.  ; NCL will change all -99.9 to 1234567.

i  = round(x,3)   ; ===>  (/-5 ,-5 ,-5 ,-4 ,-1 ,-1 , 0 ,-51, \
5 , 5 , 5 , 4 , 1 , 1 , 0 , 51, \
1234567  /)
```
Upon return, i@_FillValue = 1234567.