nobsY {Hmisc} | R Documentation

## Compute Number of Observations for Left Hand Side of Formula

### Description

After removing any artificial observations added by `addMarginal`, computes the number of non-missing observations for all left-hand-side variables in `formula`. If `formula` contains a term `id(variable)` `variable` is assumed to be a subject ID variable, and only unique subject IDs are counted. If group is given and its value is the name of a variable in the right-hand-side of the model, an additional object `nobsg` is returned that is a matrix with as many columns as there are left-hand variables, and as many rows as there are levels to the `group` variable. This matrix has the further breakdown of unique non-missing observations by `group`. The concatenation of all ID variables, is returned in a `list` element `id`.

### Usage

    nobsY(formula, group=NULL, data = NULL, subset = NULL,
          na.action = na.retain, matrixna=c('all', 'any'))

### Arguments

`formula` | a formula object
`group` | character string containing optional name of a stratification variable for computing sample sizes
`data` | a data frame
`subset` | an optional subsetting criterion
`na.action` | an optional `NA`-handling function
`matrixna` | set to `"all"` if an observation is to be considered `NA` if all the columns of the variable are `NA`, otherwise use `matrixna="any"` to consider the row missing if any of the columns are missing

### Value

an integer, with an attribute `"formula"` containing the original formula but with an `id` variable (if present) removed

### Examples

    d <- expand.grid(sex=c('female', 'male', NA),
                     country=c('US', 'Romania'),
                     reps=1:2)
    d$subject.id <- c(0, 0, 3:12)
    dm <- addMarginal(d, sex, country)
    dim(dm)
    nobsY(sex + country ~ 1, data=d)
    nobsY(sex + country ~ id(subject.id), data=d)
    nobsY(sex + country ~ id(subject.id) + reps, group='reps', data=d)
    nobsY(sex ~ 1, data=d)
    nobsY(sex ~ 1, data=dm)
    nobsY(sex ~ id(subject.id), data=dm)

[Package Hmisc version 3.17-3 Index]