> I was thrown off by the fact that after mutating it looked like the column > data type had been changed.
It was changed... in a new copy of the data frame that, because it was at the top-level interactive prompt and not being saved, was printed and then discarded. On July 25, 2020 5:11:03 PM PDT, H <age...@meddatainc.com> wrote: >On 07/25/2020 04:17 PM, Jeff Newmiller wrote: >> False. Mutate is similar in structure to the base function `within`. >Which is why you have to assign the altered data frame back onto >itself. >> >> On July 25, 2020 12:59:06 PM PDT, "Patrick (Malone Quantitative)" ><mal...@malonequantitative.com> wrote: >>> Jeff, >>> >>> mutate(), which is I think part of dplyr, also violates this, for >what >>> it's >>> worth. I suspect the breaking point is that mutate() is intended to >>> create >>> new columns in the dataframe, not alter existing ones. >>> >>> On Sat, Jul 25, 2020 at 3:52 PM Jeff Newmiller >>> <jdnew...@dcn.davis.ca.us> >>> wrote: >>> >>>> R is largely a functional language. You do something to an input >and >>> end >>>> up with an output that has no effect on the input. This is actually >a >>>> highly desirable feature. >>>> >>>> If you want your df variable to reflect changes made then you need >>> to >>>> assign your result back into it. >>>> >>>> df <- df %>% mutate(v1 = as.double(v1)) >>>> >>>> (Note that the data.table package violates this principle and is >>>> controversial as a result.) >>>> >>>> On July 25, 2020 12:11:24 PM PDT, H <age...@meddatainc.com> wrote: >>>>> In a statement like: >>>>> >>>>> df %>% mutate(v1 = as.double(v1)) >>>>> >>>>> I expect the variable v1 in dataframe df to have been converted >into >>> a >>>>> double. However, when I do: >>>>> >>>>> str(df) >>>>> >>>>> v1 still shows as int. Do I need to save the modified dataframe >>> after >>>>> mutating a variable? >>>>> >>>>> ______________________________________________ >>>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>>> PLEASE do read the posting guide >>>>> http://www.R-project.org/posting-guide.html >>>>> and provide commented, minimal, self-contained, reproducible code. >>>> -- >>>> Sent from my phone. Please excuse my brevity. >>>> >>>> ______________________________________________ >>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>> PLEASE do read the posting guide >>>> http://www.R-project.org/posting-guide.html >>>> and provide commented, minimal, self-contained, reproducible code. >>>> >Thank you, code corrected and problem solved. I was thrown off by the >fact that after mutating it looked like the column data type had been >changed. I also tried mutate_at() which similarly failed... > >______________________________________________ >R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide >http://www.R-project.org/posting-guide.html >and provide commented, minimal, self-contained, reproducible code. -- Sent from my phone. Please excuse my brevity. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
