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

[Daniel Nordlund]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Mark Knecht
> Sent: Sunday, June 28, 2009 7:32 PM
> To: Gabor Grothendieck
> Cc: r-help at r-project.org
> Subject: Re: [R] newbie - read.csv creates a (data.frame, 
> table, array, matrix, ...) and plotting one column
> 
> Thank you VERY much Gabor. I learned a LOT from this little post:
> 
> 1) I can read/modify/write data in the array using the sub function
> 2) I can address columns using $COLUMN_HEADER
> 3) I can do an XY plot using X ~ Y
> 
> Brilliant! Thanks!
> 
> Small result PDF attached.
> 
> Cheers,
> Mark
> 
> On Sun, Jun 28, 2009 at 7:04 PM, Gabor
> Grothendieck<ggrothendieck at gmail.com> wrote:
> > Try removing double quotes and commas from T1$EQUITY
> > and then convert it to numeric:
> >
> > T1$EQUITY <- as.numeric(sub('[",]', '', T1$EQUITY))
> > plot(EQUITY ~ TRADE, T1)
> >
> >
> > On Sun, Jun 28, 2009 at 9:14 PM, Mark 
> Knecht<markknecht at gmail.com> wrote:
> >> 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
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> 

Mark,

I'm glad you are making progress.  However, you are going to want to continue reading up on matrices, arrays, lists, and data frames.  What read.csv creates is a data frame which is not the same as a matrix or an array.  As you move forward you will want to keep these structues separate in your mind.

Best of luck,

Dan

Daniel Nordlund
Bothell, WA USA