[R] a question on CSV file

[Gabor Grothendieck]

Note that a CSV file is one in which data elements
are separated by commas.  There are no commas in
what you display so I assume that you are displaying
the data after you have read it in, not the CSV file.

If you read a file into a data frame x you can refer to
row i column j of the data frame as x[i,j].

The subset of rows of data frame x with column Med equal to 1 is
   x[,x$Med == 1]
or equivalently
   subset(x, Med == 1)
See ?subset for more info.

See ?save and ?write 

You can plot column heartrate vs. column ex in data frame x
like this:

plot( heartrate ~ ex, data = x )

You might find it helpful to read or re-read the document
An Introduction to R .

---
Date:   Mon, 8 Mar 2004 08:54:09 -0800 (PST) 
From:   Cindy Juncker <cindy197901 at yahoo.com>
To:   <R-help at stat.math.ethz.ch> 
Subject:   [R] a question on CSV file 

 
I have a csv file,

heartrate excercise medicine Time
12 0 0 4:30 am
23 5 0 5:00 am
34 6 0 5:30 am
56 3 0 6:00 am
24 12 1 6:30 am
35 2 0 7:00 am
26 5 0 7:30 am
63 4 0 8:00 am
24 3 1 8:30 am 
45 9 0 9:00 am

I did the folllowing:
x <- read.table("heart.csv",sep=",")
names(x) <- c("heartrate","ex","Med","Time")
x.newtime <- strptime(x$Time, format= "%H:%M %p")


What I am tring to do is: 
First I am trying to get all the data from when there was a medicine taken in previous hour.
Second I will plot heartrate VS median Excercise in previous hour.


In the first problem, how can I get the desired data? after I got it, should I put it in a new file? How? 

How can I refer to a specific cell in a csv file? 

I appreciate your kindly help!