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Learn more about Labs mapply runs into endless loop Ask Question Asked 6 years ago Modified 6 years ago Viewed 94 times Part of R Language Collective 0

I have a data.table like this:

testDT <- data.table(SFf = as.character(c("C1H1", "C3H4Cl")), Mult = as.integer(c(3,5)) )

now I am trying to loop over the rows of this table and apply a function (multiform() from the package enviPat) to it like this:

mapply(multiform,testDT$SFf,testDT$Mult)

the output of it should be two strings, namely "C3H3" and "C15H20Cl5". However the function simply never stops calculating and seems to get caught up in an endless loop.

When I apply the function like

multiform("C1H1",3)

it works and I get "C3H3" as output. What am I doing wrong?

Yasel

• r
• mapply

Share Improve this question Follow asked Dec 11, 2018 at 16:50 yaselyasel 44333 silver badges1313 bronze badges 5

• 1 Probably you are doing nothing wrong, the function multiform is just really slow. Looking at it's code it seems totally plausible that it could take a very, very long time on even moderately sized inputs. – joran Commented Dec 11, 2018 at 16:58
• when I am using it only once it takes much less than a second. but when I tried it for two rows via mapply I stopped it after 10 min, so I think that canot be it – yasel Commented Dec 11, 2018 at 17:01
• It's taking time because of the second SFf value. If you do this multiform("C3H4Cl",5), it will also take too long. – Taher A. Ghaleb Commented Dec 11, 2018 at 17:04
• If it's taking too long on only 2 elements, then yes, probably something is specifically awry with the code that handles that particular case. – joran Commented Dec 11, 2018 at 17:08
• 1 You're right, it does end up in an infinite loop for that particular example. I don't know enough about chemical formulas to debug it effectively, but it is likely that this is a bug in the function. I would contact the package authors about it and show them this example. – joran Commented Dec 11, 2018 at 17:12

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1 Answer 1

Sorted by: Reset to default Highest score (default) Trending (recent votes count more) Date modified (newest first) Date created (oldest first) 2

I got it. The problem was that the function multiform() does not allow elements without numbers behind them. So it wont take "C3H4Cl" but "C3H4Cl1".

I don't think that this is intended and will try to contact the authors of the package.

Share Improve this answer Follow answered Dec 11, 2018 at 17:15 yaselyasel 44333 silver badges1313 bronze badges 1

• I think they're aware. The "Details" section in this function's documentation says "Chemical formulas must conform to what is described in check_chemform". If you run data(isotopes); check_chemform(isotopes, 'C3H4Cl'), it will show you the corrected formula (with a 1 on the end). – IceCreamToucan Commented Dec 11, 2018 at 17:33

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