All survey questions are inherently discrete so the analyst must decide how to derive (or operationalize) that into a numeric indicator. This decision choice that rarely gets much spotlight is a difficult operation to represent in a general function.

# Factors and haven_labelled variable classes

factor is a base R variable class in which values are defined by exclusive and exhaustive list of a level and a label (See Advanced R for a brief technical overview.). Both levels and labels are necessary to track because the order in which the values were presented and what the respondent saw (the labels) matters. The levels can be thought of as fundamentally as integers, to represent the order. That said, the transformation from R factors to integers is cumbersome. ?base::factor recommends as.numeric(levels(f))[f] where f is a factor vector.

haven_labelled is a separate R class that was defined in the haven package to represent labelled variables in Stata/SPSS without loss of information. haven is a part of tidyverse and is designed to read Stata and SPSS files. Stata and SPSS have their own analogs to factors, but in Stata, these variables are literally integers/doubles with a “labels” attribute. This is a named vector where the values are the numbers and the labels are the label equivalent of factors (corresponding to Stata’s label list [lblname]). haven_labelled is a class that preserves this information (See ?haven::labelled help page or the vignette from the labelled package for more detail). For example, look at any of the variables in the CCES 2018 sample which contains a lbl tag:

gov_approval_lbl <- select(cc18_samp, case_id, CC18_308d)
gov_approval_lbl
#> # A tibble: 1,000 x 2
#>      case_id               CC18_308d
#>        <dbl>               <dbl+lbl>
#>  1 415395741 4 [Strongly disapprove]
#>  2 414164923 4 [Strongly disapprove]
#>  3 412379892 2 [Somewhat approve]
#>  4 414203529 3 [Somewhat disapprove]
#>  5 412148048 1 [Strongly approve]
#>  6 412329835 2 [Somewhat approve]
#>  7 417352072 4 [Strongly disapprove]
#>  8 414614677 1 [Strongly approve]
#>  9 416797006 1 [Strongly approve]
#> 10 412962561 1 [Strongly approve]
#> # … with 990 more rows

Recent versions of haven (>= 2.1.0) will display the labels in square brackets if the dataset is a tibble, but we can see that the values are basically doubles. If we had used factors, these numerical values would be obscured, though the levels and labels will be kept.

gov_approval_fct <- transmute(cc18_samp, case_id, CC18_308d = as_factor(CC18_308d))
gov_approval_fct
#> # A tibble: 1,000 x 2
#>      case_id CC18_308d
#>        <dbl> <fct>
#>  1 415395741 Strongly disapprove
#>  2 414164923 Strongly disapprove
#>  3 412379892 Somewhat approve
#>  4 414203529 Somewhat disapprove
#>  5 412148048 Strongly approve
#>  6 412329835 Somewhat approve
#>  7 417352072 Strongly disapprove
#>  8 414614677 Strongly approve
#>  9 416797006 Strongly approve
#> 10 412962561 Strongly approve
#> # … with 990 more rows

### Why haven_labelled is more concise

For using CCES outcomes, the haven_labelled class is more concise then factors, for the following reasons:

1. It is closer to the original format of the data as exported by YouGov (SPSS)
2. Creating derived variables via operators is more concise (think gov_approval <= 2 instead of gov_approval %in% c("Strongly approve", "approve")).

The second point is consequential. For example suppose we want to model a derived variable, Governor approval, which is 1 if the respondent strongly approves or approves of the governor. With the haven_labelled class, we can do what we would do in Stata:

gov_approval_lbl %>%
mutate(outcome = CC18_308d <= 2) %>%
count(CC18_308d, outcome)
#> # A tibble: 6 x 3
#>                  CC18_308d outcome     n
#>                  <dbl+lbl> <lgl>   <int>
#> 1  1 [Strongly approve]    TRUE      144
#> 2  2 [Somewhat approve]    TRUE      307
#> 3  3 [Somewhat disapprove] FALSE     170
#> 4  4 [Strongly disapprove] FALSE     265
#> 5  5 [Not sure]            FALSE     112
#> 6 NA                       NA          2

But this will not work with factors,

gov_approval_fct %>%
mutate(outcome = CC18_308d <= "Somewhat approve") %>%
count(outcome)
#> Warning in Ops.factor(CC18_308d, "Somewhat approve"): '<=' not meaningful for
#> factors
#> # A tibble: 1 x 2
#>   outcome     n
#> * <lgl>   <int>
#> 1 NA       1000

That means, with factors, we would need to figure out all the labels and type them up exactly as they appear. In surveys, the labels can be long and contain punctuation which is easy to miss. Of course we can extract these from attributes and save the trouble of hand-entering them, but the same information is available in the haven_labelled class too.

On the other hand, haven_labelled is a bit inconvenient because the raw number is not immediately informative. A quick way to transform the numerical data to its labels is haven::as_factor (notice this is different from base::as.factor). Or, for metadata, we can look at its attributes:

### Metadata contained in a haven_labelled variable

In the haven_labelled class, three pieces of information are stored as attributes:

1. label: Description of the entire variable (this contains a short version of the question or an indication of the question in CCES data)
2. labels: name-value pairs.

We can use str and attr to view and extract these metadata:

str(gov_approval_lbl$CC18_308d) #> 'haven_labelled' num [1:1000] 4 4 2 3 1 2 4 1 1 1 ... #> - attr(*, "label")= chr "Job approval -- The Governor of$inputstate"
#>  - attr(*, "labels")= Named num [1:7] 1 2 3 4 5 8 9
#>   ..- attr(*, "names")= chr [1:7] "Strongly approve" "Somewhat approve" "Somewhat disapprove" "Strongly disapprove" ...

For example, this indicates that CC18_308d is about "Job approval -- The Governor of $inputstate". This is not the question wording verbatim, of course. This is something that needs to be looked up in the Word Doc YouGov questionnaires each time, or in the CCES codebooks (Shiro and the CCES team has some of this in plain-text tabular form for recent years). And the possible values are attr(gov_approval_lbl$CC18_308d, "labels")
#>    Strongly approve    Somewhat approve Somewhat disapprove Strongly disapprove
#>                   1                   2                   3                   4
#>            Not sure             skipped           not asked
#>                   5                   8                   9

where again the numbers are the values and the labels attribute of the vector are the value labels.

As long as we retain these attributes (which is possible as long as haven is loaded), we can express derivation in a simple way.

# Classifying Questions by Type of Derivation

Another thing this metadata does not include is whether the response options are binary, ordinal, or categorical (no inherent ordering). This is something we need to hand-classify, although it is usually obvious once we see the question.

We consider the of the most common types below. These are from the sample question metadata (see the q_type variable):

questions_samp %>%
filter(q_ID %in% c("CC18_322C","CC18_308d", "CC18_pid3"))
#> # A tibble: 3 x 5
#>   q_ID      q_label                           cces_data q_code    response_type
#>   <chr>     <chr>                             <chr>     <chr>     <chr>
#> 1 CC18_322C Withold Sanctuary Funding         2018      CC18_322c yesno
#> 2 CC18_308d Governor Approval                 2018      CC18_308d ordinal
#> 3 CC18_pid3 Partisan Identification (3-point) 2018      pid3      categorical

This classification narrows down the type of function we would use for deriving a variable.

All three types can be derived by the basic atomic operator:

outcome = lbl_var %in% c(v1, v2, v3, ...)

where outcome is the derived variable, lbl_var the data vector of class haven_labelled, and c(v1, v2, v3, ...) is a vector of one or more in the data vector that that we consider a success.

For this project we only consider binomial models, which is why this is sufficient. Survey data is almost never continuous, and running multinomial models in MRP is still exceedingly uncommon.

## 1. Yes-No variables - use yesno_to_binary

This is the simplest case because there are only two options and it is almost always clear which of the two is naturally corresponds to a “success” instead of a “failure” in a Bernoulli random variable. That means we currently _only- use yesno_to_binary() for the derivation. For example, CC18_322C is a question asking for people’s support of a measure to withdraw federal funding for so-called “Sanctuary Cities”:

cc18_samp %>%
select(case_id, CC18_322c)
#> # A tibble: 1,000 x 2
#>      case_id   CC18_322c
#>        <dbl>   <dbl+lbl>
#>  1 415395741 2 [Oppose]
#>  2 414164923 1 [Support]
#>  3 412379892 2 [Oppose]
#>  4 414203529 1 [Support]
#>  5 412148048 2 [Oppose]
#>  6 412329835 2 [Oppose]
#>  7 417352072 2 [Oppose]
#>  8 414614677 2 [Oppose]
#>  9 416797006 1 [Support]
#> 10 412962561 1 [Support]
#> # … with 990 more rows
cc18_samp %>%
select(case_id, CC18_322c) %>%
mutate(outcome = yesno_to_binary(as_factor(CC18_322c))) %>%
count(CC18_322c, outcome)
#> # A tibble: 3 x 3
#>      CC18_322c outcome     n
#>      <dbl+lbl>   <dbl> <int>
#> 1  1 [Support]       1   466
#> 2  2 [Oppose]        0   533
#> 3 NA                NA     1

## 2. Categorical variables

These have no inherent ordering, i.e. there is no likert scale or obvious scale. These can be vote choice for parties, race, religion, or method of voting. Here we show partisanship (on a 3 point multiple choice question).

str(cc18_samp\$pid3)
#>  'haven_labelled' num [1:1000] 3 2 1 2 3 3 1 1 2 3 ...
#>  - attr(*, "label")= chr "3 point party ID"
#>  - attr(*, "labels")= Named num [1:7] 1 2 3 4 5 8 9
#>   ..- attr(*, "names")= chr [1:7] "Democrat" "Republican" "Independent" "Other" ...

To make a derived variable out of this, we need a function that takes an ordered vector of value(s) that counts as a success . For example, let’s say we want to measure the proportion of independents. Then the derivation will be

cc18_samp %>%
select(case_id, pid3) %>%
mutate(outcome = pid3 %in% 3) %>%
count(pid3, outcome)
#> # A tibble: 5 x 3
#>              pid3 outcome     n
#>         <dbl+lbl> <lgl>   <int>
#> 1 1 [Democrat]    FALSE     353
#> 2 2 [Republican]  FALSE     272
#> 3 3 [Independent] TRUE      279
#> 4 4 [Other]       FALSE      43
#> 5 5 [Not sure]    FALSE      53

because 3 stands for independent in this case, as can be seen from the metadata.

Clearly, “Yes/No” variable type can be considered a type of categorical variable type. I still distinguish these between because in the former, the analyst does not need to make a decision about what consists as a success, whereas in pid3 for example, three reasonable operations can exist and the what is a success as opposed to a failure is ambiguous from the name pid3.

## 3. Ordinal variables

Ordinal variables have a clear ordering in their labels and their values conform to that order, for example likert scales agree-disagree, approve-disagree, as well as measures like education, income, and news interest.

This means that derivation can use operators < and > instead of simply %in% – as in the Governor approval example in the beginning. We may want to lump together this with a categorical variable, but again the distinction can be meaningful because in an ordinal variable one would almost never “skip” a value, as in governor_approval %in% c(1, 3, 4), whereas in a categorical variable, one might do that depending on the order of the variables.

Note one must be careful that almost all the variables considered here are not exhaustively “ordinal” because they have “Not Sure” / “Other” / “Not Asked” values as taking values of 8 or 9. For example, because pid3 == 4 means “Other”, a derived variable defined as “pid3 >= 3” is not very meaningful unless you are interested in the group of people who identify as “Independent” or “Other”.

cc18_samp %>%
select(case_id, CC18_308d) %>%
mutate(outcome = CC18_308d <= 2) %>%
count(CC18_308d, outcome)
#> # A tibble: 6 x 3
#>                  CC18_308d outcome     n
#>                  <dbl+lbl> <lgl>   <int>
#> 1  1 [Strongly approve]    TRUE      144
#> 2  2 [Somewhat approve]    TRUE      307
#> 3  3 [Somewhat disapprove] FALSE     170
#> 4  4 [Strongly disapprove] FALSE     265
#> 5  5 [Not sure]            FALSE     112
#> 6 NA                       NA          2

# Other Considerations

Missing Values

Generic versions of derivation