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