[R] R Subset by Factor levels

[Rasmus Liland]

Dear Engin,

On 2020-07-29 16:57 +0300, Engin Yılmaz wrote:
> Dear
> 
> I try to create a new subset from my dataframe.
> My dataframe's name is m1.
> "Classification Description" column has 15 different factors.
> The following code is used creating a subset for 1 factor.
> m2<-m1[m1$`Classification Description` == levels(m1$`Classification
> Description`)[1],]
> 
> My aim is to create a subset with 4 different factors. For example,
> levels(m1$`Classification Description`)[1]
> levels(m1$`Classification Description`)[15]
> levels(m1$`Classification Description`)[2]
> levels(m1$`Classification Description`)[4]
> 
> I try to following code but it didnt work
> 
> m2<-m1[m1$`Classification Description` == levels(m1$`Classification
> Description`)[c(1,15,2,4],]

You're almost correct, you just need to 
use match instead of ==:

	m1[m1$`Classification Description` %in%
	   levels(m1$`Classification Description`)[c(1, 15, 2, 4)],]

Read more about it at ?match (?`%in%`).

Best,
Rasmus

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