CODEWITHSUNDEEP
rlapplychi-squared
Tong Zhang
Tong Zhang

Reputation: 1

How to make contingency table over a list in r

The main exposure variable is aff. I want to get contingency tables for aff and all variables in the varlist. Then I want to do chi-square test using these contingency tables. My codes are following:

name=names(data)
varlist=name[11:40]
models=lapply(varlist, function(x) {
          chisq.test(table(substitute(data$i,list(i = as.name(x))),data$aff))
 })
lapply(models, summary)

But I got error 

Error in unique.default(x, nmax = nmax) : 
  unique() applies only to vectors

How to fix this?

Upvotes: 0

Views: 691

Answers (2)

hpesoj626
hpesoj626

Reputation: 3619

Supposing your data is like mtcars, where vs, am, gear, and carb are categorical variables, you can create a function like so:

df_list_f <- function(x) chisq.test(table(df2$cyl, x))
df2 <- mtcars[,8:11] # df2 contains the columns vs, am, gear and carb
lapply(df2, df_list_f)

Upvotes: 0

r2evans
r2evans

Reputation: 160447

I think you're over-complicating things by using substitute and such. Without your data, I'll try with mtcars, using cyl as the exposure variable.

data <- mtcars
name <- names(data)
ev <- "cyl"
varlist <- name[ name != ev ]
models <- lapply(varlist, function(nm) {
  chisq.test(table(data[[nm]], data[[ev]]))
})
# Warning messages:
# 1: In chisq.test(table(data[[nm]], data[[ev]])) :
#   Chi-squared approximation may be incorrect

(because I'm using a bad example for the test, there are a lot of warnings here; this can be ignored when using mtcars because it is really not a good dataset for this test.)

summaries <- lapply(models, summary)
str(summaries[1:2])
# List of 2
#  $ : 'summaryDefault' chr [1:9, 1:3] " 1" " 1" " 1" " 1" ...
#   ..- attr(*, "dimnames")=List of 2
#   .. ..$ : chr [1:9] "statistic" "parameter" "p.value" "method" ...
#   .. ..$ : chr [1:3] "Length" "Class" "Mode"
#  $ : 'summaryDefault' chr [1:9, 1:3] " 1" " 1" " 1" " 1" ...
#   ..- attr(*, "dimnames")=List of 2
#   .. ..$ : chr [1:9] "statistic" "parameter" "p.value" "method" ...
#   .. ..$ : chr [1:3] "Length" "Class" "Mode"

Upvotes: 2

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