R help - Jan 2010 - Mutliple sets of data in one dataset....Need a loop?

Hi

I'm hoping someone can help me I am a relative newbie to R.

I have data that is in a similar format to this...

Experiment Score1 Score2
X -0.85 -0.02
X -1.21 -0.02
X  1.05  0.09
Y -1.12 -0.07
Y -0.27 -0.07
Y -0.93 -0.08
Z 1.1 -0.03
Z 2.4 0.09
Z -1.0 0.09

Now I can easily have a look at the overall correlation of score 1 and 2 by
doing this
plot(data[,2], data[,3])   or
fit <- lm(data[,2] ~ data[,3]

BUT! I really want to look at the correlations within each experiment type
so ideally a multiple plot per page of each correlation within an experiment
- and/or a way of looping through the data to get the simple linear
regression for each experiment for scores 1 and 2. This looks like an easy
example but I have thousands of results so it would be really hand to find
away of doing this quickly!!

Let me know if you need more explaining...

E
-- 
View this message in context:
http://n4.nabble.com/Mutliple-sets-of-data-in-one-dataset-Need-a-loop-tp1018503p1018503.html
Sent from the R help mailing list archive at Nabble.com.

On Jan 20, 2010, at 11:07 AM, BioStudent wrote:
>
> Hi
>
> I'm hoping someone can help me I am a relative newbie to R.
>
> I have data that is in a similar format to this...
>
> Experiment Score1 Score2
> X -0.85 -0.02
> X -1.21 -0.02
> X  1.05  0.09
> Y -1.12 -0.07
> Y -0.27 -0.07
> Y -0.93 -0.08
> Z 1.1 -0.03
> Z 2.4 0.09
> Z -1.0 0.09
>
> Now I can easily have a look at the overall correlation of score 1  
> and 2 by
> doing this
> plot(data[,2], data[,3])   or
> fit <- lm(data[,2] ~ data[,3]
>
> BUT! I really want to look at the correlations within each  
> experiment type
> so ideally a multiple plot per page of each correlation within an  
> experiment
> - and/or a way of looping through the data to get the simple linear
> regression for each experiment for scores 1 and 2. This looks like  
> an easy
> example but I have thousands of results so it would be really hand  
> to find
> away of doing this quickly!!
library(lattice)
?xyplot  # a group specification
?panel.lmline

There are quite a few examples at the xyplot help page.
>
-- 

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

You'll probably want to look at the 'by' function

d=data.frame(sex=rep(1:2,50),x=rnorm(100))
d$y=d$x+rnorm(100)
head(d)
cor(d)
by(d[,-1],d['sex'],function(df)cor(df))

You might also want to look at the doBy package
-- 
View this message in context:
http://n4.nabble.com/Mutliple-sets-of-data-in-one-dataset-Need-a-loop-tp1018503p1018616.html
Sent from the R help mailing list archive at Nabble.com.

One way to plot subsets of data identified by a grouping variable is to use
lapply() on a list of subsets.  The approach is worth mentioning because
similar tactics are useful for many problems. 

#List of unique values for grouping variable
#that is not necessarily a factor
names <- as.list(unique(df$Experiment))

#List of dataframes; 1 for each unique value of grouping variable
df.lst <- lapply(names,function(name)subset(df,Experiment==name))

#Name components of the list
#Not necessary in this case... but permits indexing by level
#of the grouping variable
names(df.lst) <- names

#Now you can use lapply() to carry out the same operation on
#each component of your list.  For example, to send plots to
#a pdf with 1 page for each component:

pdf("plot.pdf")
lapply(df.lst,function(df)plot(df[,2],df[,3]))
dev.off() 




-----
Glen Sargeant
Research Wildlife Biologist
-- 
View this message in context:
http://n4.nabble.com/Mutliple-sets-of-data-in-one-dataset-Need-a-loop-tp1018503p1018714.html
Sent from the R help mailing list archive at Nabble.com.