On Thu, Jan 31, 2013 at 10:29 AM, Weijia Wang <wwang.nyu@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
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> 174  2900     140.0      SBP
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> 176  2900     130.0      SBP
>
> 180  3900     120.0      SBP
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> 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 don’t know how to add the condition 2+ inside
> ddply.
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>
>
> Any help is appreciated!!
>
>
>
> Weijia
>
>
>

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