R: rolling correlation / non-standard evaluation - r

Question

I am trying to calculate rolling correlation on a tibble, iterating through column names in a loop. I seem to be struggling passing variables to a function, though. This works:
tbl <- tibble(date = seq(as.Date("1983-03-31"), by=7, length.out=100),
col1 = 1:100, col2 = sample(100, size = 100, replace=TRUE), col3 = col1 + col2)
tbl %>%
tq_mutate_xy(
x = col1,
y = col3,
mutate_fun = runCor,
n = 10,
use = "pairwise.complete.obs",
col_rename = "col1_col3_corr"
)
But this doesn't:
tbl <- tibble(date = seq(as.Date("1983-03-31"), by=7, length.out=100),
col1 = 1:100, col2 = sample(100, size = 100, replace=TRUE), col3 = col1 + col2)
c1 <- "col1"
c2 <- "col3"
tbl %>%
tq_mutate_xy(
x = !!c1,
y = !!c2,
mutate_fun = runCor,
n = 10,
use = "pairwise.complete.obs",
col_rename = paste0(c1, "_", c2, "_corr")
)
The error is "Error in check_x_y_valid(data, x, y) : x = !(!c1) not a valid name."
What am I doing wrong?

Answer 1

First, I think you want the non-standard evaluation (NSE) version of tq_mutate_xy --
that is, tq_mutate_xy_. As a result, when you use the NSE of these functions, you need to use character strings -- this means your mutate_fun variable should also be a character string. The following should work:
c1 <- "col1"
c2 <- "col3"
tbl %>%
tq_mutate_xy_(
x = c1,
y = c2,
mutate_fun = "runCor",
n = 10,
use = "pairwise.complete.obs",
col_rename = paste0(c1, "_", c2, "_corr")
)
Be sure to look at example 5 from the help documentation, ?tq_mutate_xy