ggvis - custom non-numeric y-axis labels showing as 'NaN' - r

Question

EDIT: Sample code updated with more complex example
I have a data frame with (x, y) values and a name for each pair, and I'm plotting it in a ggvis scatterplot. SO users already pointed me to this post (How do I label plot tick marks using ggvis) and I updated my code to reflect what I saw there by using factor() to create the list of custom y-axis labels ylabels_ which is fed to values = under the add_axis() statement. Here is the new code:
library(stringi)
require(ggvis)
set.seed(13)
df <- data.frame(x = 1:15,
y = c(rep.int(1, 15),
rep.int(4, 15),
rep.int(7, 15)))
ylabels_ <- factor(c(1,4,7), labels = stri_rand_strings(3, 7))
df %>%
ggvis(~x, ~y) %>%
add_axis("y", values = ylabels_)
My axis labels are still coming back with NaN instead of the factors. Am I missing something?
SOLUTION EDIT: Here is my code that I finally got to work. Note I changed the x values to be staggered so I could distinguish between the three lines.
library(stringi)
require(ggvis)
set.seed(13)
df <- data.frame(x = c(seq(1, length.out = 15, by = 3),
seq(2, length.out = 15, by = 3),
seq(3, length.out = 15, by = 3)),
y = factor(c(rep.int(1, 15),
rep.int(4, 15),
rep.int(7, 15)), labels = c("one", "four", "seven"),
ordered = T))
df %>%
ggvis(~x, ~y) %>%
layer_points() %>%
scale_ordinal("y", domain = c("seven", "four", "one")
I don't understand why in the domain = portion I had to reverse the order of the factors for them to show in the correct order. If anyone has any insight on that, it would be very helpful!

Answer 1

Notice that in the linked answer, the new factor variable is used as the y variable. You can use it for your values, as well, but it's not necessarily needed.
Making the new factor based on y but using name as the labels is to get the name variable in the correct order for plotting.
df$ylabels_ <- factor(df$y, labels = stri_rand_strings(3, 7))
Because you are now working with a factor variable on the y axis, layer_points needs to be used explicitly.
df %>%
ggvis(~x, ~ylabels_) %>%
layer_points()
Note that this whole approach will only work if the original y data are integers.

Answer 2

Call me a fool, but I'm calling this a bug (which, BTW, is not answering your question):
## set up data
lab <- factor(1:15, labels=stri_rand_strings(15, 7))
val <- 1:15
## all works according to expectations on the "x" axis
data.frame(xx=lab, yy=val) %>%
ggvis(~xx, ~yy) %>%
layer_points() %>%
add_axis("x", values=lab,
properties=axis_props(labels=list(angle=90, fontSize = 10)))
## nothing works according to expectations on the "y" axis
## attempt 1
data.frame(xx=val, yy=lab) %>%
ggvis(~xx, ~yy) %>%
layer_points() %>%
add_axis("y", values=lab,
properties=axis_props(labels=list(angle= 0, fontSize = 10)))
## attempt 2
data.frame(xx=val, yy=as.numeric(val)) %>%
ggvis(~xx, ~yy) %>%
layer_points() %>%
add_axis("y", values=lab,
properties=axis_props(labels=list(angle= 0, fontSize = 10)))