[R] Issue replacing dataset values from read data

[William Michels]

1. It's not immediately clear why you need the line "temp <- subset(df, id
== myid)"

2. The objects described by "temp$age", temp$agesmoke, and temp$yrsquit are
all vectors. So temp.yrssmoke is also a vector. This means that when you
replace, it should be with "<- temp.yrssmoke[i]", where "i" is the (row)
 number you're looping over (note "temp" re-numbers rows to 1 through 6,
another reason to remove the "temp" line).

3. Ditto for " <- (temp$cigsdaytotal[i]/20)*(temp.yrssmoke[i]) "

Hope this helps!

Bill

W. Michels, Ph.D.



On Fri, May 6, 2016 at 3:19 PM, Chang, Emily <Emily.Chang2 at ucsf.edu> wrote:

> Dear all,
>
> I am reading a modest dataset (2297 x 644) with specific values I want to
> change. The code is inelegant but looks like this:
>
> df <- read.csv("mydata.csv", header = TRUE, stringsAsFactors = FALSE)
>
> # yrsquit, packyrs missing for following IDs. Manually change.
> for(myid in c(2165, 2534, 2553, 2611, 2983, 3233)){
>      temp <- subset(df, id == myid)
>      df[df$id == myid , "yrsquit"] <- 0
>      temp.yrssmoke <- temp$age-(temp$agesmoke+temp$yrsquit)
>      df[df$id == myid , "yrssmoke"]  <- temp.yrssmoke
>      df[df$id == myid , "packyrs"] <-
> (temp$cigsdaytotal/20)*(temp.yrssmoke)
> }
>
> If I run just the first line and then the for loop, it works.
> If I run the first line and for loop together, yrsquit is properly
> replaced to == 0, but packyrs is NA still.
>
> Obviously there's many ways around this specific problem, but I was
> wondering what the issue is here, so as to look out for and avoid it in the
> future.
>
> Apologies for the lack of reproducible code; I haven't yet reproduced the
> problem with generated data.
>
> Much thanks in advance.
>
> Best regards,
> Emily
>
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>
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