[R] newbie - read.csv creates a (data.frame, table, array, matrix, ...) and plotting one column

Mark Knecht
Mon, 29 Jun 2009 01:14:51 -0000

On Sun, Jun 28, 2009 at 4:02 PM, Mark Knecht<markknecht at gmail.com>
wrote:
> Hi all,
> ? Newbie alert.
<SNIP>
>
> ? The second question is about plotting one column from data set.
> I've used read.csv to read in somethign called PFA_VWAP. row.names,
> names and dim all return sensible values. The command
> PFA_VWAP_Equity<-PFA_VWAP[,10] seems to load the new variable with the
> right data for the equity curve, but how do I plot it?
> plot(PFA_VWAP_Equity) gives me a chart that doesn't make sense to me.
> Note however that the original values that make up column 10 were
> surrounded by quotes so I'm not sure how to tell what sort of data R
> thinks is in column 10. Is it numeric or text? I think it's integer
> from the last command.
<SNIP>

So I've tried to boil this down to the something simple others can try
and duplicate my confusion, or just see what's going on from this
post.

Basically I'm trying to get a handle on the difference between a list
and an array, and how to take my data read with read.csv and plot it
on a scatter chart.

1) Here's a small portion of one of my data files. I put this at
C:\Test1.csv

PORTFOLIO EQUITY TABLE
TRADE,MARK-SYS,DATE/TIME,PL/SIZE,PS METHOD,POS SIZE,POS
PL,DRAWDOWN,DRAWDOWN(%),EQUITY
1,1,1/9/2004 1:11:00 PM,-146.00,As
Given,1,-146.00,146.00,1.460,"9,854.00"
2,1,1/12/2004 1:11:00 PM,874.00,As Given,1,874.00,0.00,0,"10,728.00"
3,1,1/13/2004 1:11:00 PM,224.00,As Given,1,224.00,0.00,0,"10,952.00"
4,1,1/28/2004 12:28:00 PM,-626.00,As
Given,1,-626.00,626.00,5.716,"10,326.00"
5,1,2/9/2004 1:11:00 PM,64.00,As
Given,1,64.00,562.00,5.131,"10,390.00"
6,1,2/13/2004 1:11:00 PM,-116.00,As
Given,1,-116.00,678.00,6.191,"10,274.00"
7,1,2/20/2004 1:11:00 PM,364.00,As
Given,1,364.00,314.00,2.867,"10,638.00"
8,1,2/23/2004 11:23:00 AM,-626.00,As
Given,1,-626.00,940.00,8.583,"10,012.00"
9,1,2/24/2004 1:11:00 PM,114.00,As
Given,1,114.00,826.00,7.542,"10,126.00"
10,1,2/25/2004 1:11:00 PM,444.00,As
Given,1,444.00,382.00,3.488,"10,570.00"

(In case of line breakage everything from TRADE to EQUITY is on line 2
and there are 10 lines that follow making 12 lines total.)

2) I read this into R creating T1 using the command

T1<-read.csv("C:\\Test1.csv",skip=1,header=TRUE)

3) If I type T1 and hit return then I see the data.

4) dim(T1) says 10 10 which is correct.

5) I can read the two columns I want to use to create the scatter plot using:

> T1[,1]
 [1]  1  2  3  4  5  6  7  8  9 10
> T1[,10]
 [1] 9,854.00  10,728.00 10,952.00 10,326.00 10,390.00 10,274.00
10,638.00 10,012.00 10,126.00 10,570.00
Levels: 10,012.00 10,126.00 10,274.00 10,326.00 10,390.00 10,570.00
10,638.00 10,728.00 10,952.00 9,854.00
>

Now, here's the confusion. plot(T1[,1],T1[,10]) creates a plot, but
the range on both X & Y is 1-10. I want 1-10 on the X axis but need
the values in the first line of the T1[,10] return as the Y axis.

How can I create that scatter plot?

Thanks,
Mark