n.show argument in `plotFilterValues` ignored

[albersonmiranda]

I'm working on a data set with several features and just noticed plotFilterValues is ignoring n.show argument. Code inspected, couldn't find how it should work.

I ran something like
importance = generateFilterValuesData(train.task, method = "FSelectorRcpp_information.gain") plotFilterValues(importance, n.show = 10)
and got all features, instead of 10.

Changed line 188 on the file for
data = fvalues$data %>% arrange(desc(value)) %>% slice(1:n.show)
and it seems to do the trick.

Could you guys check it?

Edit by @pat-s: Reprex added

library(mlr)
#> Loading required package: ParamHelpers

importance = generateFilterValuesData(spam.task, method = "FSelectorRcpp_information.gain")
plotFilterValues(importance, n.show = 10)

^{Created on 2019-12-03 by the reprex package (v0.3.0)}

[larskotthoff]

Ah, yes, that is a bug. Fixing this will be trickier than the code you're proposing though as there's also an argument that allows to specify the order. This is only used to reorder values in the plot though, not to actually sort the data.

The documentation doesn't specify what values are selected...

I think it probably makes most sense here to sort the values, select the top n, and then plot in that order (and change the documentation accordingly). Other opinions @pat-s ?

[albersonmiranda]

@larskotthoff when you say 'sort the values', you mean that sort argument would not reorder values in the plot, but actually sort data meaning to select top n most important or the top n least important features?
Or keep sort for the plot only and sort the data always in descending way, as i did above?

There could even be both sort and reorder arguments, one for data and another for the plot, with default descending for both (which makes more sense to me).

[larskotthoff]

I mean sort the data. That would make most sense here I think -- reordering it just for the plot doesn't make it as obvious what's happening.

[pat-s]

@albersonmiranda Thanks. For an unknown reason, n.show was not used at all in plotFilterValues().