[R] Unexpected behavior when giving a value to a new variable based on the value of another variable

[jim holtman]

You are being bitten by the "partial matching" of the "$" operator
(see  ?"$" for a better explanation).  Here is solution that works:


**original**
> N <- structure(list(V1 = c(67, 62, 74, 61, 60, 55, 60, 59, 58), V2 = c(NA, 1, 1, 1, 1,1,1,1,NA)),
+                     .Names = c("age","samplem"), row.names = c(NA,
-9L), class = "data.frame")
> N$sample[N$age >= 65] <- 1
> N
  age samplem sample
1  67      NA      1
2  62       1      1
3  74       1      1
4  61       1      1
5  60       1      1
6  55       1      1
7  60       1      1
8  59       1      1
9  58      NA     NA
>
>
> N <- structure(list(V1 = c(67, 62, 74, 61, 60, 55, 60, 59, 58), V2 = c(NA, 1, 1, 1, 1,1,1,1,NA)),
+                     .Names = c("age","samplem"), row.names = c(NA,
-9L), class = "data.frame")
> N[["sample"]][N$age >= 65] <- 1  # use the '[[' operation for complete matching
> N
  age samplem sample
1  67      NA      1
2  62       1     NA
3  74       1      1
4  61       1     NA
5  60       1     NA
6  55       1     NA
7  60       1     NA
8  59       1     NA
9  58      NA     NA

Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.


On Fri, Aug 29, 2014 at 4:53 AM, Angel Rodriguez
<angel.rodriguez at matiainstituto.net> wrote:
>
> Dear subscribers,
>
> I've found that if there is a variable in the dataframe with a name very similar to a new variable, R does not give the correct values to this latter variable based on the values of a third value:
>
>
>> M <- structure(list(V1 = c(67, 62, 74, 61, 60, 55, 60, 59, 58)),.Names = c("age"), row.names = c(NA, -9L),
> +                class = "data.frame")
>> M$sample[M$age >= 65] <- 1
>> M
>   age sample
> 1  67      1
> 2  62     NA
> 3  74      1
> 4  61     NA
> 5  60     NA
> 6  55     NA
> 7  60     NA
> 8  59     NA
> 9  58     NA
>> N <- structure(list(V1 = c(67, 62, 74, 61, 60, 55, 60, 59, 58), V2 = c(NA, 1, 1, 1, 1,1,1,1,NA)),
> +                     .Names = c("age","samplem"), row.names = c(NA, -9L), class = "data.frame")
>> N$sample[N$age >= 65] <- 1
>> N
>   age samplem sample
> 1  67      NA      1
> 2  62       1      1
> 3  74       1      1
> 4  61       1      1
> 5  60       1      1
> 6  55       1      1
> 7  60       1      1
> 8  59       1      1
> 9  58      NA     NA
>
>
>
> Any clue for this behavior?
>
>
>
> My specifications:
>
> R version 3.1.1 (2014-07-10)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
>
> locale:
> [1] LC_COLLATE=Spanish_Spain.1252  LC_CTYPE=Spanish_Spain.1252    LC_MONETARY=Spanish_Spain.1252
> [4] LC_NUMERIC=C                   LC_TIME=Spanish_Spain.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] foreign_0.8-61
>
> loaded via a namespace (and not attached):
> [1] tools_3.1.1
>
>
>
>
> Thank you very much.
>
> Angel Rodriguez-Laso
> Research project manager
> Matia Instituto Gerontologico
>
>
>         [[alternative HTML version deleted]]
>
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