R: Evaluate an Expression in a Data Environment

with {base} | R Documentation

## Evaluate an Expression in a Data Environment

### Description

Evaluate an R expression in an environment constructed from data.

### Usage

    with(data, expr, ...)

### Arguments

`data` | data to use for constructing an environment. For the default method this may be an environment, a list, a data frame, or an integer as in `sys.call`.
`expr` | expression to evaluate.
`...` | arguments to be passed to future methods.

### Details

`with` is a generic function that evaluates `expr` in a local environment constructed from `data`. The environment has the caller's environment as its parent. This is useful for simplifying calls to modeling functions.

### See Also

`evalq`.

### Examples

    #examples from glm:

    library(MASS)
    data(anorexia)
    with(anorexia, {
        anorex.1 <- glm(Postwt ~ Prewt + Treat + offset(Prewt),
                        family = gaussian)
        summary(anorex.1)
    })

    with(data.frame(u = c(5,10,15,20,30,40,60,80,100),
                    lot1 = c(118,58,42,35,27,25,21,19,18),
                    lot2 = c(69,35,26,21,18,16,13,12,12)),
        list(summary(glm(lot1 ~ log(u), family=Gamma)),
             summary(glm(lot2 ~ log(u), family=Gamma))))

    # example from boxplot:
    data(ToothGrowth)
    with(ToothGrowth, {
        boxplot(len ~ dose, boxwex = 0.25, at = 1:3 - 0.2,
                subset= supp == "VC", col="yellow",
                main="Guinea Pigs' Tooth Growth",
                xlab="Vitamin C dose mg",
                ylab="tooth length", ylim=c(0,35))
        boxplot(len ~ dose, add = TRUE, boxwex = 0.25, at = 1:3 + 0.2,
                subset= supp == "OJ", col="orange")
        legend(2, 9, c("Ascorbic acid", "Orange juice"),
               fill = c("yellow", "orange"))
    })

    # alternate form that avoids subset argument:
    with(subset(ToothGrowth, supp == "VC"),
         boxplot(len ~ dose, boxwex = 0.25, at = 1:3 - 0.2,
                 col="yellow", main="Guinea Pigs' Tooth Growth",
                 xlab="Vitamin C dose mg",
                 ylab="tooth length", ylim=c(0,35)))
    with(subset(ToothGrowth,  supp == "OJ"),
         boxplot(len ~ dose, add = TRUE, boxwex = 0.25, at = 1:3 + 0.2,
                 col="orange"))
    legend(2, 9, c("Ascorbic acid", "Orange juice"),
           fill = c("yellow", "orange"))

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