Insert "" instead of NA when adding rows in gdf [gWidgets2RGtk2] - r

Question

Is it possible to insert "" instead of NA when creating a new row in gdf?
EDIT: Here's some sample code that I tried
require(gWidgets2RGtk2)
df <- data.frame(x=1:5,y=6:10) #Sample data frame
w2 <- gwindow("keyfile editor")
h <- gdf(df,cont=w2)
addHandlerChanged(h, handler = function(h,...){ #Handler to remove NA
h<<-apply(h[1:nrow(h),1:ncol(h)], 2, function(x) gsub("NA","",x))
})

Answer 1

svalue(h$obj, drop = FALSE)
gives you the new value for the updated row. So in theory,
addHandlerChanged(h, handler = function(h,...) {
svalue(h$obj, drop = FALSE)[] <- lapply(
svalue(h$obj, drop = FALSE),
function(x) {
x[is.na(x)] <- ""
}
)
}
should replace all the NAs with "". There are two problems:
Firstly, replacing the missing values with an empty string converts the whole column to be a character vector, which you probably don't want, and secondly, there seems to be a problem with svalue<- that means the values aren't updating.
I think that the problem is this:
methods(`svalue<-`)
## [1] svalue<-.default* svalue<-.GCheckbox* svalue<-.GFormLayout* svalue<-.GGroup*
## [5] svalue<-.GHtml* svalue<-.GLabel* svalue<-.GMenuBar* svalue<-.GRadio*
## [9] svalue<-.GToolBar* svalue<-.GTree*
shows that there is no GDf-specific method for setting the svalue, so svalue<-.default will be called.
gWidgets2:::`svalue<-.default`
## function (obj, index = NULL, ..., value)
## {
## if (!isExtant(obj)) {
## return(obj)
## }
## if (getWithDefault(index, FALSE))
## obj$set_index(value, ...)
## else obj$set_value(value, ...)
## obj
## }
This calls the object's set_value method.
ls(attr(h, ".xData"))
## [1] "add_cell_popup" "add_popup_to_view_col" "add_to_parent"
## [4] "add_view_columns" "block" "block_editable_column"
## [7] "cell_popup_id" "change_signal" "clear_stack"
## [10] "clear_view_columns" "cmd_coerce_column" "cmd_insert_column"
## [13] "cmd_remove_column" "cmd_replace_column" "cmd_set_column_name"
## [16] "cmd_set_column_names" "cmd_stack" "coerce_with"
## [19] "connected_signals" "default_cell_popup_menu" "default_expand"
## [22] "default_fill" "default_popup_menu" "freeze_attributes"
## [25] "get_column_index" "get_column_value" "get_dim"
## [28] "get_name" "get_view_column" "handler_id"
## [31] "initFields" "initialize" "initialize#GComponent"
## [34] "initialize#GWidget" "invoke_change_handler" "invoke_handler"
## [37] "is_editable" "map_j" "model"
## [40] "not_deleted" "notify_observers" "parent"
## [43] "set_editable" "set_frame" "set_name"
## [46] "set_names" "set_parent" "store"
## [49] "toolkit" "unblock_editable_column" "widget"
but there doesn't seem to be one implemented yet.

Answer 2

Well, Richie did his usual thorough job. This question has a few problems: One you use the variable h as a global variable (for the gdf object) and as the argument to the handler, so within the handler h does not refer to the object, but h$obj would. Second To set values for selection in the gdf object uses the [<- method (h[i,j] <- "" calls the h object's set_items method). You tried to modify the object, not call a method on it. As for NA values, underlying the items to select from is an RGtk2DataFrame, which like a data frame in R will coerce values to character if you try to put a character value into a numeric value. Best, to use R as it is intended. If you really want to get rid of NA values you can do so when you go to use the values that the user has edited, modifying h[,] as you want.
Now, if you really wanted to do this, I think you could at the RGtk2 level by writing an appropriate cell renderer.