Problem with grouped psych::alpha within the do::dplyr/tidyverse and broom::tidy

Question

I have survey data performed using the same questionnaire in different languages. I would like to write an elegant dplyr/tidyverse code for the reliability for each language, using psych::alpha within. Let's imagine, that the data frame (df) looks like that:

I want to calculate item and scale reliability for Q_1:Q_6, for each group indicated by the group_var variable and the code I wrote looks like this

require(tidyverse)
require(psych)
require(broom)

    df %>% 
      select(group_var, Q_1:Q_6) %>%
      as.data.frame() %>% 
      group_by(group_var) %>% 
      do(tidy(psych::alpha(c(Q_1:Q_6))))

but when I run the code, I got an error message:

Error in psych::alpha(c(Q_1:Q_6)) : 
  object 'Q_1' not found

What is wrong with the code? Thanks in advance.

StupidWolf · Answer 1 · 2020-05-21T13:05:57.270

I don't think tidy works on psych::alpha(), using an example:

r4 <- sim.congeneric()
tidy(alpha(r4))
Error: No tidy method for objects of class psych

So tidy is out of question, unless there is a Best thing you can do is wrap them up in a list within a tibble:

library(dplyr)
library(tidyr)
library(purrr)
library(psych)
library(broom)

df = data.frame(group_var=sample(LETTERS[1:6],100,replace=TRUE),
matrix(sample(0:3,900,replace=TRUE),nrow=100))
colnames(df)[-1] = c(paste0("Q_",1:6), paste0("V_", 23:25))

res = df %>% 
select(group_var, Q_1:Q_6) %>%
nest(data=Q_1:Q_6) %>%
mutate(alpha = map(data,
~alpha(.x,keys=c("Q_1","Q_2","Q_3","Q_4","Q_5","Q_6"))
))

res$alpha[[1]]

Reliability analysis   
Call: alpha(x = .x, keys = c("Q_1", "Q_2", "Q_3", "Q_4", "Q_5", "Q_6"))

  raw_alpha std.alpha G6(smc) average_r   S/N ase mean   sd median_r
     -0.37      -0.3    0.13     -0.04 -0.23 0.6  1.6 0.36    0.039

 lower alpha upper     95% confidence boundaries
-1.54 -0.37 0.81 

 Reliability if an item is dropped:
     raw_alpha std.alpha G6(smc) average_r      S/N alpha se var.r  med.r
Q_1-     -0.38  -0.38221  -0.143  -0.05854 -0.27652     0.61 0.028 -0.080
Q_2-     -0.21  -0.19042   0.173  -0.03305 -0.15996     0.54 0.048  0.066
Q_3-     -0.38  -0.26988   0.096  -0.04439 -0.21252     0.61 0.053  0.046
Q_4-     -0.54  -0.41760  -0.064  -0.06261 -0.29458     0.68 0.045 -0.016
Q_5-     -0.35  -0.26006   0.154  -0.04305 -0.20639     0.60 0.058  0.059
Q_6-      0.03  -0.00088   0.107  -0.00018 -0.00088     0.42 0.024 -0.016

 Item statistics 
      n raw.r std.r  r.cor r.drop mean   sd
Q_1- 13  0.42  0.45  0.552 -0.062 0.77 1.01
Q_2- 13  0.38  0.33 -0.073 -0.162 1.85 1.14
Q_3- 13  0.39  0.38  0.083 -0.058 1.92 0.95
Q_4- 13  0.45  0.47  0.416  0.050 1.62 0.87
Q_5- 13  0.33  0.38 -0.039 -0.073 2.08 0.86
Q_6- 13  0.21  0.18 -0.137 -0.309 1.38 1.12

Non missing response frequency for each item
       0    1    2    3 miss
Q_1 0.08 0.15 0.23 0.54    0
Q_2 0.38 0.23 0.23 0.15    0
Q_3 0.31 0.38 0.23 0.08    0
Q_4 0.15 0.38 0.38 0.08    0
Q_5 0.38 0.31 0.31 0.00    0
Q_6 0.15 0.38 0.15 0.31    0

A quick check seems tidystats might be able to do it, but I ran the example code and doesn't seem to work. So you can try it for yourself.

Thank you very much. The code you proposed returns an error after the running of `res = tibble(df) %>% select(group_var, Q_1:Q_6) %>% nest(data=Q_1:Q_6) %>% mutate(alpha = map(data, ~alpha(.x,keys=c("Q_1","Q_2","Q_3","Q_4","Q_5","Q_6")) ))` `Error in .f(.x[[i]], ...) : object 'group_var' not found` — Jakhongir Alidjanov, May 21 '20 at 13:03
sorry i realize there is a package clash. can you restart your session and use only tidyr, purrr and dplyr like my edited answer? don't load the full tidyverse — StupidWolf, May 21 '20 at 13:07
I have bit modified your code for the avoidance of a multiplication of the data frames in the environment. Now it looks like this: `(df%>% select(id.study.group, Q_1:Q_6) %>% nest(data=Q_1:Q_6) %>% mutate(cronbach=map(data, ~alpha(.x, keys = (c("Q_1", "Q_2", "Q_3", "Q_4", "Q_4", "Q_5", "Q_6"))))))$cronbach` — Jakhongir Alidjanov, May 21 '20 at 15:25
adding `summary` between `~` and `alpha` displayes summary statistics for all groups at one sight. — Jakhongir Alidjanov, May 21 '20 at 15:31

Problem with grouped psych::alpha within the do::dplyr/tidyverse and broom::tidy

1 Answers1