On Thu, Jan 31, 2013 at 10:29 AM, Weijia Wang <wwang....@gmail.com> wrote:
> Hi,
>
>
>
> I have a new question about subsetting in R.
>
>
>
> Say we have this data frame:
>
>
>
> PT_ID Blood_Pressure OBS_TYPE
>
> 92 1900 90.0 DBP
>
> 94 1900 90.0 DBP
>
> 174 2900 140.0 SBP
>
> 176 2900 130.0 SBP
>
> 180 3900 120.0 SBP
>
> 268 3900 150.0 SBP
>
> 268 3900 90.0 DBP
>
>
>
> I need to obtain those with 2+ DBP>=90 or 2+ SBP>=140.
>
>
>
> PT_ID=1900, he has 2 DBP>=90, so he will be included.
>
> PT_ID=2900, he has 1 SBP>=140, so he will NOT be included.
>
> PT_ID=3900, he has 1 SBP>=140 and 1 DBP>=90, so he will still NOT be
> included.
>
>
>
> So, the condition requires TWO OR MORE values higher than the threshold.
> It could be either SBP or DBP or both of them.
>
>
>
> I have tried ddply, but I dont know how to add the condition 2+ inside
> ddply.
>
>
>
> Any help is appreciated!!
>
>
>
> Weijia
>
>
>
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