[R] Delete rows from data.frame matching a certain criteria

[Ista Zahn]

Hi,

On Mar 1, 2012, at 12:38 PM, Sarah Goslee wrote:

> Hi,
> 
> On Thu, Mar 1, 2012 at 11:11 AM, mails <mails00000 at gmail.com> wrote:
>> Hello,
>> 
>> 
>> consider the following data.frame:
>> 
>> test <- data.frame(n = c(1,2,3,4,5), v = c(6,5,7,5,3), pattern =
>> c(1,1,NA,1,NA))
>> 

< snip >

>> So basically the result should look like this:
>>> test
>>  n v pattern
>> 1  1     NA       1
>> 2  2     NA      1
>> 3  3     7      NA
>> 4  4     NA       1
>> 5  5     3      NA
> 
>> So far, I solved it by creating subsets and using merge but it turns out to
>> be super slow. Is there a way to do that
>> with the apply function?
> 
> Far too much work. What about:
> 
>> test$v <- ifelse(test$pattern == 1, NA, v)
>> test
>  n  v pattern
> 1 1 NA       1
> 2 2 NA       1
> 3 3 NA      NA
> 4 4 NA       1
> 5 5 NA      NA

Actually that doesn't work because of those pesky missing values. You need

test <-  transform(test, v = ifelse(pattern == 1 & !is.na(pattern), NA, v))

Best,
Ista

> 
> 
> -- 
> Sarah Goslee
> http://www.functionaldiversity.org
> 
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