I have a function that looks like this:
removeRows <- function(dataframe, rows.remove){
dataframe <- dataframe[-rows.remove,]
print(paste("The", paste0(rows.remove, "th"), "row was removed from", "xxxxxxx"))
}
I can use the function like this to remove the 5th row from the dataframe:
removeRows(mtcars, 5)
The function output this message:
"The 5th row was removed from xxxxxxx"
How can I replace xxxxxxx with the name of the dataframe I have used, so in this case mtcars?
You need to access the variable name in an unevaluated context. We can use substitute for this:
removeRows <- function(dataframe, rows.remove) {
df.name <- deparse(substitute(dataframe))
dataframe <- dataframe[rows.remove,]
print(paste("The", paste0(rows.remove, "th"), "row was removed from", df.name))
}
In fact, that is its main use; as per the documentation,
The typical use of
substituteis to create informative labels for data sets and plots.
substitute is essentially a hack. You can however inspect the call stack in Python – it might be able to retrieve the parameter name through that but it’s going to be more complex since you’ll have to retrieve and inspect the calling context’s byte code.loginfo(expression) instead of loginfo("expression: %s" % expression)... -- Just found it: In Python, there is another option to achieve this: github.com/lihaoyi/macropy#tracingI would like to point out that df.name <- deparse(substitute(dataframe)) should be used at the top of your function before any transformation is done. I used it right at the end of my function, just before doing ggsave, which does not return the name but somehow what is inside the dataframe, which is not what you want. This gave me a lot of headache.
So something like this :
function(df){
df.name <- deparse(substitute(dataframe))
ggplot()
ggsave()
}
dataframe <- dataframe[rows.remove,]does not propagate changes outside the function call? Also,rows.removeis supposed to be negative.-rows.remove. Sorry, don't understand what you mean by 'does not propagate changes outside the function call'. This is my fault, not yours. Could you expand please?removeRowsas it stands now, R will create a copy of yourdataframeand modify the copy. When the function terminates, the (modified) copy is destroyed, and the originaldataframewill be untouched. If you want to change the original data, you must call it asmtcars <- removeRows(mtcars, 5)AND add the linedataframe(orreturn(dataframe)) at the end of the function code.