how add values in a data frame after a for loop?

Question

I have a dataset with an ID column and Value column and I ran the Shapiro Wilk test in order to check the normality of the different values in the ID column regarding their values in the Value column. What I want to do is to create a data frame that will have 4 columns. The first will be the name of the ID, the second will be the W value and the third will be the p-value. The fourth column will have values non- normal /normal or accept H1 depending on the p-values. This is the dput

dput(df)
structure(list(ID = c("F1", "F1", "F1", "F1", "F1", "F1", "F1", 
"F2", "F2", "F2", "F2", "F2", "F2", "F2", "F2", "F3", "F3", "F3", 
"F3", "F3", "F3", "F3", "F3", "F3", "F4", "F4", "F4", "F4", "F4", 
"F4", "F4", "F4"), Values = c(9.6, NA, 10.2, 9.8, 9.9, 9.9, 9.9, 
1.2, 1.2, 1.8, 1.5, 1.5, 1.6, 1.4, NA, 3266, 3256, 7044, 6868, 
NA, 3405, 3410, NA, 5567, 59.4, 56, 52.8, 52.4, 55.5, NA, NA, 
53.6)), class = "data.frame", row.names = c(NA, -32L))

This is what I have done so far in order to run the test of all the IDs and an effort to create a data frame.

install.packages("data.table")
library(data.table)

uniq_id <- unique(df$ID)

number_loops <- length(uniq_id)

headings <- c("ID", "Wilk", "p_value","Accept H1")



df_table <- as.data.frame(matrix(NA, nrow = (number_loops ), ncol = length(headings)))



for(i in unique(df$ID)){
  u <- setDT(df)[ID == i]
  s <- shapiro.test(u$Values)
  print(i)
  print(s)
}

To improve your chance of a response, I would start here: stackoverflow.com/help/someone-answers — Dave2e
– Dave2e, Commented Aug 5, 2021 at 0:28

Parfait · Accepted Answer · 2021-08-05 00:45:05Z

1

Consider by to subset data by unique values of column(s) and runs a function on each subset where you can run the needed test and extract results to data.table. Afterwards, bind all data subset results together:

dt_list <- by(df, df$ID, function(sub) {
    results <- shapiro.test(sub$Values)

    data.table(
        ID = sub$ID[1],
        Wilk = results$statistic,
        p_value = results$p.value,
        accept_H1 = results$p.value <= 0.05
   )
})

dt_table <- data.table::rbindlist(dt_list)

answered Aug 5, 2021 at 0:45

Parfait

108k19 gold badges103 silver badges138 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

how add values in a data frame after a for loop?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related