Hi,
I think there are two easy ways to fix this. The first is to use a `switch`
to call the intended function, this should not be a problem since there are
a small number of print functions in **mixR**
```R
print.mixfitEM <- function (x, digits = getOption("digits"), ...)
{
switch(x$family,
gamma = printgamma (x, digits),
lnorm = printlnorm (x, digits),
normal = printnormal (x, digits),
weibull = printweibull(x, digits),
stop(gettextf("invalid '%s' value", "x$family", domain = "R")))
invisible(x)
}
environment(print.mixfitEM) <- getNamespace("mixR")
print.mixfitEM <- compiler::cmpfun(print.mixfitEM)
```
This is nice because 'x' is no longer evaluated twice (you could try this
yourself with something like
`mixR:::print.mixfitEM(writeLines("testing"))`, you'll see the output
twice, once for `x$family` and a second for evaluating `match.call()`
expression), it follows standard evaluation, and 'x' is returned invisibly
at the end, like most other `print` methods. If you really wanted to
continue using `eval`, you could instead do something like
```R
print.mixfitEM <- function (x, digits = getOption("digits"), ...)
{
expr <- quote(printfunction(x, digits))
expr[[1L]] <- as.symbol(paste0("print", x$family))
eval(expr)
invisible(x)
}
environment(print.mixfitEM) <- getNamespace("mixR")
print.mixfitEM <- compiler::cmpfun(print.mixfitEM)
```
This also solves the same issues, but it's ugly and slower.
At least for now, I would copy one of the functions above into the
site-wide startup profile file or your user profile, along with
```R
utils::assignInNamespace("print.mixfitEM", print.mixfitEM, "mixR")
```
This does have the unfortunate side effect of loading **mixR** every time
an R session is launched, but you could also put it inside another function
like:
```R
fix.mixR.print.mixfitEM <- function ()
{
print.mixfitEM <- function(x, digits = getOption("digits"), ...) {
switch(x$family,
gamma = printgamma (x, digits),
lnorm = printlnorm (x, digits),
normal = printnormal (x, digits),
weibull = printweibull(x, digits),
stop(gettextf("invalid '%s' value", "x$family", domain = "R")))
invisible(x)
}
environment(print.mixfitEM) <- getNamespace("mixR")
print.mixfitEM <- compiler::cmpfun(print.mixfitEM)
utils::assignInNamespace("print.mixfitEM", print.mixfitEM, "mixR")
}
```
which you would then call in your scripts before using **mixR**. I hope
this helps!
On Thu, May 25, 2023 at 10:19 AM Sarah Goslee <sarah.gos...@gmail.com>
wrote:
Hi,
I ran into a problem with S3 method dispatch and scoping while trying
to use functions from the mixR package within my own functions. I know
enough to find the problem (I think!), but not enough to fix it
myself. The problem isn't really a package-specific problem, so I'm
starting here, and will file an issue with the maintainer once I have
a solution.
Detailed explanation below, but briefly, the S3 methods in this
package use match.call() and then eval() to select the correct
internal method. This works fine from the command line, but if the
method is called from within another function, the use of
environment() within eval() means that the objects passed to the
wrapper function are no longer visible within the eval() call.
I have a two-part question:
A. How do I get around this right now?
B. What would the correct approach be for the package authors?
library(mixR)
# first example from ?mixfit
## fitting the normal mixture models
set.seed(103)
x <- rmixnormal(200, c(0.3, 0.7), c(2, 5), c(1, 1))
data <- bin(x, seq(-1, 8, 0.25))
fit1 <- mixfit(x, ncomp = 2) # raw data
rm(x, data)
###
# simple function
funworks <- function(x) {
print(x)
}
###
# almost identical simple function
funfails <- function(thisx) {
print(thisx)
}
###
funworks(fit1)
funfails(fit1)
#######
The explanation as I understand it...
print called on this object gets passed to print.mixfitEM(), which is:
function (x, digits = getOption("digits"), ...)
{
family <- x$family
mc <- match.call()
mc$digits <- digits
fun.name <- paste0("print", family)
mc[[1]] <- as.name(fun.name)
eval(mc, environment())
}
Working through the calls, when eval() is called from within funfails(),
mc is
printnormal(x = thisx, digits = 7)
and the calling environment does not contain thisx.
In funworks(), it's
printnormal(x = x, digits = 7)
and x is found.
So, I can get around the problem by naming my argument x, as in
funworks(), but that's unsatisfying. Is there something else I can do
to get my functions to work?
And what's the correct way to do what print.mixfitEM() is doing, so
that it works regardless? I poked around for a while, but didn't find
a clear (to me!) answer.
Thanks,
Sarah
--
Sarah Goslee (she/her)
http://www.numberwright.com
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