[R] Locate Patients who have multiple high blood pressure readings

[Bert Gunter]

Well, since no one has responded....


Please use ?dput to provide data in your posts.

 There are likely  zillions of way to go about this. Following is one
way based on ?duplicated that I think works, but I make no claims for
either elegance or efficiency. Others may do lots better. But maybe it
suffices.


## Untested
## I assume the data is provided in a data frame named dd.

## All PT_ID's with >=1 high readings in SBP or in DBP
> hiS <- with(dd,PT_ID[OBS_TYPE == "SBP" & Blood_Pressure >= 140])
> hiD <-  with(dd,PT_ID[OBS_TYPE == "DBP" & Blood_Pressure > =90])

## id's that appear more than once in either
> union(unique(hiS[duplicated(hiS)]), unique(hiD[duplicated(hiD)])

## you can subset your data frame to match just these,  e.g. via
%in%, if you like.


Cheers,
Bert




On Thu, Jan 31, 2013 at 7:51 AM, Weijia Wang <wwang.nyu at gmail.com> wrote:
> On Thu, Jan 31, 2013 at 10:29 AM, Weijia Wang <wwang.nyu at 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 don’t know how to add the condition 2+ inside
>> ddply.
>>
>>
>>
>> Any help is appreciated!!
>>
>>
>>
>> Weijia
>>
>>
>>
>
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>
>
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-- 

Bert Gunter
Genentech Nonclinical Biostatistics

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