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Louis da Silva
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Asked: 2022-05-18T11:02:30+00:00 In:

Error: invalid type (list) for variable – quick tips

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As advised, I used some code samples in another forum, but it could not improve the problem. My question is the “invalid type (list) for variable” in r – How to solve it? The command line is:

data <- read.table("usedcar.dat", row.names = 1)
 young <- data[1,]
 med <- data[2,]
 old <- data[3,]
 Price <- c(young, med, old)
 Age <- as.factor(c(rep(1,12), rep(2,12), rep(3,12)))
 data <- cbind(Age, Price)
 data <- as.data.frame(data)

 replicate(12, rnorm(3))

 str(data)
 'data.frame': 36 obs. of 2 variables:
  $ Age :List of 36
  ..$ 1 : int 1
  ..$ 2 : int 1
  ..$ 3 : int 1
  ...
  ..$ 36: int 3
  $ Price:List of 36
  ..$ 1 : int 2300
  ...
  ..$ 36: int 2075

and the result:

m1 <- aov(Price ~ Age, data = data)
 Error in model.frame.default(formula = Price ~ Age, data = data, drop.unused.levels = TRUE) : invalid type (list) for variable 'Price'

What does the message mean? Can you advise me to fix it? If you have other better answers, leave them in the answer box below.

invalid type for variable
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2 Answers

  1. Best Answer
    Expert

    The cause: Because data frames’ default rows are lists, but not numeric vectors. When you read.table(), you obtain a data frame (Therefore, creating a matrix won’t change anything).

    data <- as.data.frame(matrix(rnorm(36),nrow=3))
young <- data[1,]; med <- data[2,]; old <- data[3,]
Price <- c(young, med, old)
str(Price)
## ## List of 36
## ## $ V1 : num 0.648
## ## $ V2 : num 0.157
## ## ...

    Solution: The issue is that this is a list rather than a numeric vector. So, Unlist() is a simple technique to deal with this:

    dd <- data.frame(Age,Price=unlist(Price))
aov(Price~Age,dd)
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  2. invalid type (list) for variable x is an error message that lm and other formula-based functions give. It indicates that x was not expecting a vector but instead a list. The str(data_frame_name$x) result is a standard way to debug the error. data_frame_name is the data frame containing x. You will usually find x not the data type you expected.

    • 24

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