[R] Establishing groups using something other than ifelse()

[Duncan Murdoch]

On 12-01-19 6:05 PM, Sam Albers wrote:
> Hello all,
>
> This is one of those "Is there a better way to do this questions". Say
> I have a dataframe (df) with a grouping variable (z). This is my base
> data. Now I know that there is a higher order level of grouping that
> exist for my group variable. So what I want to do is create a new
> column that express that higher order level of grouping based on
> values in the sub-group (z  in this case). In the past I have used
> ifelse() but this tends to get fairly redundant and messy with a large
> amount of sub-groupings (z). I've created a sample dataset below. Can
> anyone recommend a better way of achieving what I am currently
> achieving with ifelse()? A long series of ifelse statements makes me
> think that there is something better for this.
>
> ## Dataframe creation
> df<- data.frame(x=runif(36, 0, 120),
>                         y=runif(36, 0, 120),
>
> z=factor(c("A1","A1","A2","A2","B1","B1","B2","B2","C1","C","C2","C2"))
>                         )
>
> ## Current method is grouping
> df$Big.Group<- with(df, ifelse(df$z=="A1","A", ifelse(df$z=="A2","A",
> ifelse(df$z=="B1", "B", ifelse(df$z=="B2", "B", "C")))))
>
>
> So any suggestions? Thanks in advance!

Use a named vector, e.g.

newcodes <- c(A1="A", A2="A", ... etc.

Then Big.Group <- newcodes[as.character(z)]

Duncan Murdoch