create dataframe in for loop using dataframe array - r

Question

I'm having a dataframe as like below. I need to extract df based on the region which is availabe in RL
>avg_data
region SN value
beta 1 32
alpha 2 44
beta 3 55
beta 4 60
atp 5 22
> RL
V1
1 beta
2 alpha
That dataframe should be in array something like REGR[beta] which should contain beta related information as like below
region SN value
beta 1 32
beta 3 55
beta 4 60
Similarly for REGR[alpha]
region SN value
alpha 2 44
So that I can pass REGR as a argument for plotting graph.
REGR <- data.frame()
for (i in levels(RL$V1)){
REGR[i,] <- avg_data[avg_data$region==i, ];
}
I did some mistake in the above code. Please correct me.. Thank you

Answer 1

The split function may be of interest to you. From the help page, split divides the data in the vector x into the groups defined by f.
So for your data, it may look something like:
> split(avg_data, avg_data$region)
$alpha
region SN value
2 alpha 2 44
$atp
region SN value
5 atp 5 22
$beta
region SN value
1 beta 1 32
3 beta 3 55
4 beta 4 60
If you want to filter out the records that do not occur in RL, I'd probably do that in a preprocessing step using the %in% function and [ for extraction:
x <- avg_data[avg_data$region %in% RL$V1,]
#-----
region SN value
1 beta 1 32
2 alpha 2 44
3 beta 3 55
That's what I'd feed to split if you want to drop atp.
The approach above may be overkill if you are just wanting to plot. Here's an example using sapply to iterate through each level of region and make a plot:
sapply(unique(x$region), function(z)
plot(x[x$region == z,"value"], main=z[1]))