sd_show_if(
# Simple condition based on single question choice
input$penguins1 == "other" ~ "penguins1_other",
# Multiple condition based on multiple question choices
input$penguins2 == "other" & input$show_other == "show" ~ "penguins2_other"
)
Common Conditions
The sd_show_if()
function to conditionally display a question and the sd_skip_forward()
function to conditionally skip to a page each require that you provide a condition that returns a logical value (TRUE
or FALSE
) for each condition. This page highlights some of the most common types of conditions you might need.
While we use the sd_show_if()
function in most of these examples, the same logic applies to conditions used in the sd_skip_forward()
function.
Conditioning on question answers
One of the most common situations is conditioning on the value of a single question or multiple questions, like this:
In the first condition, the penguins1
question is checked to see if the respondent chose the "other"
option. If they did, the penguins1_other
question will be shown.
In the second condition, the penguins2
question is checked to see if the respondent chose the "other"
option, and the show_other
question is checked to see if the respondent chose the "show"
option. With this condition, the penguins2_other
question will only be shown if both conditions are TRUE
.
Numeric values
Another common condition is checking the value of a numeric question. To do so, you need to wrap the input$question_id
in the as.numeric()
function because all question values are stored as strings, like this:
sd_show_if(
as.numeric(input$car_number) > 1 ~ "car_ownership"
)
In the condition above, the car_number
question is checked to see if the respondent chose a number greater than 1. If they did, the car_ownership
question will be shown.
Multiple response questions
For multiple response question types (e.g. mc_multiple
), the question returns a vector storing all the chosen values. You can use this vector to check for different conditions, such as whether the chosen values are in some set of values using the %in%
operator, or whether the respondent chose a number of options using the length()
function, like this:
In the first example, the fav_fruits
question is checked to see if the respondent chose "apple"
, "banana"
, or both; if so, the apple_or_banana
question will be shown.
In the second example, the fav_fruits
question is checked to see if the respondent chose more than 3 fruits; if so, the fruit_number
question will be shown.
Conditioning on answered status
You may want to show a target question if a question is answered at all or not. To do this, we created the sd_is_answered()
function that returns TRUE
if a question is answered and FALSE
otherwise.
For example, let’s say you had a multiple choice question fav_fruit
that asked you to choose your favorite fruit from a list of options, and a target question num_fruit
that asked how many fruit you eat per day. If we wanted to show the num_fruit
question so long as the fav_fruit
question is answered, we can use sd_is_answered("fav_fruit")
in the sd_show_if()
function, like this:
sd_show_if(
sd_is_answered("fav_fruit") ~ "num_fruit"
)
This way, as long as the fav_fruit
question is answered, no matter which option the user picks the num_fruit
question will appear.
For "matrix"
type questions, sd_is_answered()
will only be TRUE
if all sub-questions (matrix rows) in it are answered.
Conditioning with custom functions
For situations where the conditional logic is more complex, we recommend defining a custom function that will return a logical value (TRUE
or FALSE
). You can then pass this function to the sd_show_if()
or sd_skip_forward()
functions as a condition.
For example, let’s say we had a mc
type question where we asked how many cars the respondent owned, and we included numeric options 1
through 5
as well as a final option "6 or more"
. If we wanted to set a condition that would return TRUE
if the user had more than one car, using as.numeric(input$question_id) > 1
as the condition would be problematic, because this would return NA
if the respondent chose the "6 or more"
option.
To address this, we could create a custom function to handle this special condition:
server <- function(input, output, session) {
more_than_one_car <- function(input) {
if (is.null(input$car_number)) {
return(FALSE)
}
num_cars <- suppressWarnings(as.numeric(input$car_number))
if (is.na(num_cars)) {
return(TRUE)
}
return(num_cars > 1)
}
sd_show_if(
more_than_one_car(input) ~ "car_ownership"
)
sd_server(db = db)
}
In the more_than_one_car()
function, we first return FALSE
if the question is not yet answered (that’s the if (is.null(input$car_number))
part). Then we obtain the numeric value of the car_number
question using as.numeric(input$car_number)
. We included a suppressWarnings()
call here only because R will warn you if the result is NA
by coercion. This will only happen if the respondent chose the "6 or more"
option, in which case we return TRUE
. If not, then we return the simple condition num_cars > 1
since we can safely know that the value of num_cars
is a number.
Conditioning on custom values
Sometimes you’ll want to condition on values that aren’t directly related to question responses. For example, you might want to randomly assign respondents to different survey versions or experimental conditions.
Let’s say you have two versions of a page, e.g. page2a
and page2b
, and you want half of your respondents to see page 2a and the other half to see page 2b. You can accomplish this by:
- Generating a random condition value
- Storing that value for later use
- Using
sd_skip_forward()
to direct respondents to the appropriate page
Here’s how to implement this:
server <- function(input, output, session) {
# Generate random condition
a_or_b <- sample(c('a', 'b'), 1)
# Store the condition value for later use if needed
sd_store_value(a_or_b)
# Use sd_skip_forward to direct to either page2a or page2b based on condition
sd_skip_forward(
a_or_b == 'a' ~ 'page2a',
a_or_b == 'b' ~ 'page2b'
)
sd_server()
}
In this example, sample(c('a', 'b'), 1)
randomly selects either 'a'
or 'b'
. The sd_store_value()
function saves this value to the database, making it available for later analysis. Then, sd_skip_forward()
uses this value to determine which page version the respondent should see.
This approach can be also be used for sd_show_if()
. For example, here is how you could randomly assign a question to be hidden or shown:
server <- function(input, output, session) {
# Create a static value to control question visibility
show_condition <- sample(c(TRUE, FALSE), 1)
# Store the static value for display in the UI
sd_store_value(show_condition, "show_condition")
# Show the conditional question based on the static value
sd_show_if(
show_condition ~ "conditional_question"
)
sd_server()
}
Conditioning on reactive expressions
The same behavior as the above example for conditioning on custom values can also be achieved using reactive expressions, using the sd_reactive()
function. In this example, we define a reactive expressions, a_or_b
, and then use it to control the conditional page skipping.
Note here that the conditions must be defined using a_or_b()
instead of a_or_b
- this is because in this example this object is a reactive expression rather than a static value and must be evaluated like a function call.
Note also that we don’t have to explicitly store the value in our data with a call to sd_store_value()
. This is because the sd_reactive()
function automatically stores the value in the data and will save it according to the specified id
(in this case, "a_or_b"
).
server <- function(input, output, session) {
a_or_b <- sd_reactive("a_or_b", {
sample(c('a', 'b'), 1)
})
# Use sd_skip_forward to direct to either page2a or page2b based on condition
sd_skip_forward(
a_or_b() == 'a' ~ 'page2a',
a_or_b() == 'b' ~ 'page2b'
)
sd_server()
}
shiny::shinyApp(ui = sd_ui(), server = server)
Likewise, the same concept can be applied to conditionally displaying a question based on a reactive expression:
server <- function(input, output, session) {
# Create a reactive value that will control question visibility
show_condition <- sd_reactive("show_condition", {
sample(c(TRUE, FALSE), 1) # Randomly choose TRUE or FALSE
})
# Show the conditional question based on the reactive value
sd_show_if(
show_condition() ~ "conditional_question"
)
sd_server()
}