[R] simple loop(?) analysing subsets

[karmakiller]

Hi All,

I have a large data set with many columns of data. One of these columns is a
species identifier and the remainder are variables such as temperature or
mass. Currently I am carrying out a single regression on subsets of the data
set, e.g. separated data sets with only the data from one species at a time.
I have been searching for a thread that will help me to understand how best
to repeat this process for each different species identifier in that
variable column. I can’t seem to find one that is similar to what I am
trying to do. It might be the case that I am not looking for the right thing
or that I do not fully understand the process.

How do I run a simple loop that produces a regression for each species as
identified in the variable species id, which is one column in the large data
set that I am using?

Simple regression that I wish to repeat

data<- read.table("…/STUDY.txt",header=T)
names(data)
model<- with(data,{lm(o2con~bm)})
summary(model)


sample data set

species id 	o2con	    bm
1		0.5	    5
1		0.6	    2
1		0.4	    4
1		0.4	    2
1		0.5	    3
2		0.3	    7
2		0.4	    8
2		0.5	    3
2		0.7	    4
2		0.9	    2
3		0.3	    6
3		0.7	    2
3		0.4	    1
3		0.3	    7
5		0.3	    2
5		0.6 	    1
5		0.9	    7
5		0.2	    5

I would be very grateful for some help with this. I really like using R and
I can usually figure out what I want to do but I have been trying to figure
this out for a while now and I am getting nowhere. 

Thank you.

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