[R] if statement problem

[Christos Hatzis]

You need to use '&' instead of '&&':

A shorter version of your code using ifelse:

das$danger <- with(das, ifelse(age>65 & bmi>30, 1, 0))

HTH

-Christos 

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Gerard Smits
> Sent: Tuesday, January 01, 2008 5:04 PM
> To: r-help at r-project.org
> Subject: [R] if statement problem
> 
> Hi All,
> 
> I have a small dataset named das  (43 cases) in which I am 
> trying to create a binary outcome (1/0) based on the following code:
> 
> if (das$age>65 && das$bmi>30) {das$danger<-1} else das$danger<-0
> 
> I am setting a flag called 'danger' to 1 of the subject is 
> over 65 and has a BMI > 30.
> 
> I find that my statement evaluates the first record in the 
> data.frame and then carries that assignment for all. I 
> detected this as I played around with the values and found 
> that the T/F status of the first record was always carried 
> dowqn. I have gotten this to work with an elseif 
> construction, but would like to know what is happening here.
> 
> Thanks,
> 
> Gerard
> 
> Using: Windows Vista and R 2.61
> 
> 
> Code and output:
> 
> das<- sasxport.get("c:\\personal\\r\\das.xpt")
> if (das$age>65 && das$bmi>30) {das$danger<-1} else das$danger<-0
> attach(das)
> das
> 
> 
>          The following object(s) are masked from das ( position 3 ) :
> 
>           age bmi day id male sex status
> 
>        id age sex  bmi status day male danger
> 1  33001  35   M 27.5      0 365    1      0
> 2  33002  29   M 34.9      1  22    1      0
> 3  33003  41   F 23.6      0 365    0      0
> 4  33004  55   F 27.0      0 365    0      0
> 5  42001  37   M 39.0      0 365    1      0
> 6  42002  53   M 26.6      1 124    1      0
> 7  42003  46   F 45.4      1 287    0      0
> 8  42004  35   F 36.2      0 365    0      0
> 9  42005  38   F 24.6      0 365    0      0
> 10 42006  58   F 28.0      0 365    0      0
> 11 42007  27   M 25.0      0 365    1      0
> 12 42008  65   F 24.6      0 365    0      0
> 13 42009  25   F 28.0      0 365    0      0
> 14 43001  66   M 27.8      0 365    1      0
> 15 43002  57   F 34.0      0 365    0      0
> 16 43003  45   F 38.1      0 365    0      0
> 17 43004  33   F 53.3      1  62    0      0
> 18 43005  56   F 36.5      0 365    0      0
> 19 43006  31   F 22.4      1   1    0      0
> 20 43007  53   F 32.2      1  21    0      0
> 21 55001  51   M 29.2      0 365    1      0
> 22 55002  33   F 18.7      0 365    0      0
> 23 55003  40   F 30.3      0 365    0      0
> 24 55004  67   M 31.9      0 365    1      0 <- Problem case should 
> =1 for danger
> 25 55005  41   F 35.0      0 365    0      0
> 26 55006  44   F 37.3      0 365    0      0
> 27 55007  67   M 28.4      1   1    1      0
> 28 55008  65   F 28.8      0 365    0      0
> 29 55009  76   M 18.8      1 225    1      0
> 30 55010  75   F 21.1      1  39    0      0
> 31 63001  30   F 24.9      0 365    0      0
> 32 63002  36   F 47.2      1 377    0      0
> 33 63003  45   F 32.0      0 365    0      0
> 34 63004  49   F 32.3      0 365    0      0
> 35 63005  41   F 20.2      0 365    0      0
> 36 63006  60   F 28.2      0 365    0      0
> 37 63007  33   F 24.5      0 365    0      0
> 38 63008  36   F 28.4      1  56    0      0
> 39 63009  31   F 22.1      0 365    0      0
> 40 63010  77   M 26.6      1   9    1      0
> 41 63011  41   F 32.0      0 365    0      0
> 42 63012  40   F 38.5      1  92    0      0
> 43 63013  27   M 20.6      0 365    1      0
> 
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