shifts: Shift Data (i.e., lag/lead)
In quest: Prepare Questionnaire Data for Analysis

Description Usage Arguments Details Value See Also Examples

shifts shifts rows of data down (n < 0) for lags or up (n > 0) for leads replacing the undefined data with a user-defined value (e.g., NA). The number of rows shifted is equal to abs(n). It is assumed that data[vrb.nm] is already sorted by time such that the first row is earliest in time and the last row is the latest in time.

1	shifts(data, vrb.nm, n, undefined = NA, suffix)

`data`	data.frame of data.
`vrb.nm`	character vector of colnames from `data` specifying the variables.
`n`	integer vector of length 1. Specifies the direction and magnitude of the shift. See details.
`undefined`	atomic vector of length 1 (probably makes sense to be the same typeof as the vectors in `data[vrb.nm]`). Specifies what to insert for undefined values after the shifting takes place. See details.
`suffix`	character vector of length 1 specifying the string to append to the end of the colnames of the return object. The default depends on the `n` argument: 1) if `n` < 0, then `suffix` = `paste0("_g", -n)`, 2) if `n` > 0, then `suffix` = `paste0("_d", +n)`, 3) if `n` = 0, then `suffix` = "".

If n is negative, then shifts inserts undefined into the first abs(n) rows of data[vrb.nm], shifting all other rows of x down abs(n) positions, and then dropping the last abs(n) row of data[vrb.nm] to preserve the original nrow of data. If n is positive, then shifts drops the first abs(n) rows of x, shifting all other rows of data[vrb.nm] up abs(n) positions, and then inserts undefined into the last abs(n) rows of x to preserve the original length of data. If n is zero, then shifts simply returns data[vrb.nm].

It is recommended to use L when specifying n to prevent problems with floating point numbers. shifts tries to circumvent this issue by a call to round within shifts if n is not an integer; however that is not a complete fail safe. The problem is that as.integer(n) implicit in shifts truncates rather than rounds.

data.frame of shifted data with colnames specified by suffix.

shift shifts_by shift_by