glm `predict()` error: no applicable method for 'predict' applied to an object of class "list"

Question

我在控制输入预测函数的对象类型时遇到问题。这是我生成 glm 对象的简化函数。

fitOneSample <- function(x,data,sampleSet)
{
  #how big of a set are we going to analyze? Pick a number between 5,000 & 30,000, then select that many rows to study
  sampleIndices <- 1:5000

  #now randomly pick which columns to study
  colIndices <- 1:10

  xnames <- paste(names(data[,colIndices]),sep = "")
  formula <- as.formula(paste("target ~ ", paste(xnames,collapse = "+")))
  glm(formula,family=binomial(link=logit),data[sampleIndices,])
}

myFit <- fitOneSample(1,data,sampleSet)
fits <- sapply(1:2,fitOneSample,data,sampleSet)
all.equal(myFit,fits[,1]) #different object types

#this works
probability <- predict(myFit,newdata = data)

#this doesn't
probability2 <- predict(fits[,1],newdata = data)
# Error in UseMethod("predict") :
# no applicable method for 'predict' applied to an object of class "list"

如何访问 fits[,1] 中的列，以便使用预测函数获得与 myFit 相同的结果？

Answer 1

我想我现在可以恢复你的情况了。

fits <- sapply(names(trees),
               function (y) do.call(lm, list(formula = paste0(y, " ~ ."), data = trees)))

以内置数据集trees为例，拟合三个线性模型：

Girth ~ Height + Volume
Height ~ Girth + Volume
Volume ~ Height + Girth

由于我们使用了 sapply，并且每次迭代 returns 相同的 lm 对象或长度为 12 的列表，结果将简化为 12 * 3矩阵：

class(fits)
# "matrix"

dim(fits)
# 12  3

矩阵索引 fits[, 1] 有效。

如果您检查 str(fits[, 1])，它几乎看起来像一个普通的 lm 对象。但是如果你进一步检查：

class(fits[, 1])
# "list"

嗯？它没有 "lm" class! 因此， S3 dispatch 方法在调用泛型函数时会失败 predict:

predict(x)
#Error in UseMethod("predict") : 
#  no applicable method for 'predict' applied to an object of class "list"

这可以看作是sapply具有破坏性的一个很好的例子。我们想要lapply，或者至少，sapply(..., simplify = FALSE)：

fits <- lapply(names(trees),
               function (y) do.call(lm, list(formula = paste0(y, " ~ ."), data = trees)))

lapply的结果更容易理解。它是一个长度为 3 的列表，其中每个元素都是一个 lm 对象。我们可以通过 fits[[1]] 访问第一个模型。现在一切正常了：

class(fits[[1]])
# "lm"

predict(fits[[1]])
#        1         2         3         4         5         6         7         8 
# 9.642878  9.870295  9.941744 10.742507 10.801587 10.886282 10.859264 10.957380 
#        9        10        11        12        13        14        15        16 
#11.588754 11.289186 11.946525 11.458400 11.536472 11.835338 11.133042 11.783583 
#       17        18        19        20        21        22        23        24 
#13.547349 12.252715 12.603162 12.765403 14.002360 13.364889 14.535617 15.016944 
#       25        26        27        28        29        30        31 
#15.628799 17.945166 17.958236 18.556671 17.229448 17.131858 21.888147

您可以通过

修复您的代码

fits <- lapply(1:2,fitOneSample,data,sampleSet)
probability2 <-predict(fits[[1]],newdata = data)

glm `predict()` error: no applicable method for 'predict' applied to an object of class "list"

glm `predict()` error: no applicable method for 'predict' applied to an object of class "list"

regression

r

predict

glm