R中的更新函數和變量訪問

Question

我需要更新函數內部的模型公式。這是一個例子：

A <- runif(n = 200)    # generate some data 
B <- runif(n = 200) 
P <- 1/(1+exp(.5-A))   # generate event probability 
outcome <- runif(n = 200) < P # generate outcome 

my.function <- function(model, data.to.add) { # this is the function for updating the formula 
    new.model <- update(object = model, formula. = ~ . + data.to.add) 
    return (new.model) 
} 

test <- my.function(model = glm(outcome ~ B, family = binomial(link="logit")), data.to.add = A) 

不幸的是這代碼的執行提出了這樣的錯誤：

Error in eval(expr, envir, enclos) : object 'data.to.add' not found 

似乎my.function不能提供可變data.to.add的價值update功能。我可以做些什麼來給另一個函數內的update函數提供正確的變量範圍？

編輯：好的，如果要傳遞給要更新的函數的變量位於全局環境中，那麼現在如果我必須在函數內部定義變量，那麼您的解決方案會很好，變量：

A <- runif(n = 200)    # generate some data 
P <- 1/(1+exp(.5-A))   # generate event probability 
outcome <- runif(n = 200) < P # generate outcome 

nested.update<-function(model) { 
    B<-runif(n = 200) 
    my.function <- function(model, data.to.add) { # this is the function for updating the formula 
    data.to.add <- paste('. ~ . +', deparse(substitute(data.to.add)), sep = "") 
    new.model <- update(object = model, formula. = data.to.add) 
    return (new.model) 
    } 
    return(my.function(model = model, data.to.add = B)) 
} 

nested.update(model = glm(outcome ~ A, family = binomial(link="logit"))) 

Answer 1

編輯

my.function <- function(model, data.to.add) { # this is the function for updating the formula 
    data.to.add <- sprintf('. ~ . + %s', deparse(substitute(data.to.add))) 
    new.model <- update(object = model, formula. = data.to.add) 
    return (new.model) 
} 

my.function(lm(mpg ~ wt, data = mtcars), disp) 

# Call: 
# lm(formula = mpg ~ wt + disp, data = mtcars) 
# 
# Coefficients: 
# (Intercept)   wt   disp 
#  34.96055  -3.35083  -0.01772 

my.function(lm(mpg ~ wt, data = mtcars), hp) 

# Call: 
# lm(formula = mpg ~ wt + hp, data = mtcars) 
# 
# Coefficients: 
# (Intercept)   wt   hp 
#  37.22727  -3.87783  -0.03177 

---

不好回答：

由於您將公式傳遞給update，因此R正在調度update.formula而不是默認的update.default。參數名稱是old和new。在update.default中，名稱分別爲model和formula.，就像您現在使用的那樣。

而且採用一個變通，以獲得正確的變量名稱代入公式

my.function <- function(model, data.to.add) { # this is the function for updating the formula 
    data.to.add <- sprintf('. ~ . + %s', deparse(substitute(data.to.add))) 
    new.model <- update(old = model, new = data.to.add) 
    return (new.model) 
} 

my.function(y ~ a, b) 
# y ~ a + b 
my.function(y ~ a, c) 
# y ~ a + c