zoo (version 1.1-1)

na.approx: Replace NA by Interpolation

Description

Generic functions for replacing each NA with interpolated values.

Usage

na.approx(object, ...) 
## S3 method for class 'default':
na.approx(object, along = index(object), na.rm = TRUE, ...) 

na.spline(object, ...) 
## S3 method for class 'default':
na.spline(object, along = index(object), na.rm = TRUE, ...)

Arguments

object

object in which NAs are to be replaced

along

variable to use for interpolation. Has to be numeric, is otherwise coerced to numeric.

na.rm

logical. Should leading NAs be removed?

...

further arguments passed to methods.

Value

• An object in which each NA in the input object is replaced by interpolating the non-NA values before and after it. Leading NAs are omitted (if na.rm = TRUE) or not replaced (if na.rm = FALSE).

Details

Missing values (NAs) are replaced by linear interpolation via approx or cubic spline interpolation via spline, respectively. By default the index associated with object is used for interpolation. Note, that if this calls index.default this gives an equidistant spacing 1:NROW(object). If object is a matrix or data.frame, the interpolation is done separately for each column.

See Also

zoo, approx, spline

Examples

z <- zoo(c(2,NA,1,4,5,2), c(1,3,4,6,7,8))

## use underlying time scale for interpolation
na.approx(z) 
## use equidistant spacing
na.approx(z, 1:6)

na.approx(zoo(c(NA,9,3,2,3,2)))